Bone mineral density changes among women initiating blood pressure lowering drugs: a SWAN cohort study.

SUMMARY: We examined the effect of blood pressure lowering drugs on BMD using data from the Study of Women's Health Across the Nation. Thiazide users had a slower decline in BMD compared to nonusers, while decline among ACE inhibitor and beta blocker users were similar to rates in nonusers. INTRODUCTION: Several blood pressure lowering drugs may affect bone mineral density (BMD), leading to altered fracture risk. We examined the effect of blood pressure lowering drugs on BMD using data from the Study of Women's Health Across the Nation. METHODS: We conducted a propensity score matched cohort study. Women were initiators of ACE inhibitors (ACEi), beta-blockers (BB), or thiazide diuretics (THZD). Their annualized BMD changes during the 14 years of observation were compared with nonusers. RESULTS: Among the 2312 eligible women, we found 69 ACEi, 71 BB, and 74 THZD users who were matched by a propensity score with the same number of nonusers. THZD users had a slower annual percent decline in BMD compared to nonusers at the femoral neck (FN) (-0.28% vs -0.88%; p = 0.008) and the spine (-0.74% vs -1.0%; p = 0.34), albeit not statistically significant. Annual percent changes in BMD among ACEi and BB users were similar to rates in nonusers. In comparison with BB, THZD use was associated with a trend toward less annualized BMD loss at the spine (-0.35% vs -0.60%; p = 0.08) and a similar trend at the FN (-0.39% vs -0.64%; p = 0.08); in comparisons with ACEi, THZD was also associated with less loss at the FN (-0.48% vs -0.82%; p = 0.02), but not at the spine (-0.40% vs -0.56%; p = 0.23). CONCLUSIONS: Neither ACEi nor BB was associated with improvements in BMD. THZD use was associated with less annualized loss of BMD compared with nonusers, as well as compared with ACEi and BB.

Young adults with cystic fibrosis have altered trabecular microstructure by ITS-based morphological analysis.

UNLABELLED: Young adults with cystic fibrosis have compromised plate-like trabecular microstructure, altered axial alignment of trabeculae, and reduced connectivity between trabeculae that may contribute to the reduced bone strength and increased fracture risk observed in this patient population. INTRODUCTION: The risk of fracture is increased in patients with cystic fibrosis (CF). Individual trabecular segmentation (ITS)-based morphological analysis of high-resolution peripheral quantitative computed tomography (HR-pQCT) images segments trabecular bone into individual plates and rods of different alignment and connectivity, which are important determinants of trabecular bone strength. We sought to determine whether alterations in ITS variables are present in patients with CF and may help explain their increased fracture risk. METHODS: Thirty patients with CF ages 18-40 years underwent DXA scans of the hip and spine and HR-pQCT scans of the radius and tibia with further assessment of trabecular microstructure by ITS. These CF patients were compared with 60 healthy controls matched for age (±2 years), race, and gender. RESULTS: Plate volume fraction, thickness, and density as well as plate-plate and plate-rod connectivity were reduced, and axial alignment of trabeculae was lower in subjects with CF at both the radius and the tibia (p < 0.05 for all). At the radius, adjustment for BMI eliminated most of these differences. At the tibia, however, reductions in plate volume fraction and number, axially aligned trabeculae, and plate-plate connectivity remained significant after adjustment for BMI alone and for BMI and aBMD (p < 0.05 for all). CONCLUSIONS: Young adults with CF have compromised plate-like and axially aligned trabecular morphology and reduced connectivity between trabeculae. ITS analysis provides unique information about bone integrity, and these trabecular deficits may help explain the increased fracture risk in adults with CF not accounted for by BMD and/or traditional bone microarchitecture measurements.

Defects in cortical microarchitecture among African-American women with type 2 diabetes.

SUMMARY: Patients with type 2 diabetes mellitus (DM2) have increased fracture risk. We found that African-American women with DM2 have increased cortical porosity and lower cortical bone density at the radius than non-diabetic controls. These cortical deficits are associated with hyperglycemia and may contribute to skeletal fragility associated with DM2. INTRODUCTION: Fracture risk is increased in patients with type 2 diabetes mellitus (DM2) despite normal areal bone mineral density (aBMD). DM2 is more common in African-Americans than in Caucasians. It is not known whether African-American women with DM2 have deficits in bone microstructure. METHODS: We measured aBMD at the spine and hip by DXA, and volumetric BMD (vBMD) and microarchitecture at the distal radius and tibia by HR-pQCT in 22 DM2 and 78 non-diabetic African-American women participating in the Study of Women Across the Nation (SWAN). We also measured fasting glucose and HOMA-IR. RESULTS: Age, weight, and aBMD at all sites were similar in both groups. At the radius, cortical porosity was 26% greater, while cortical vBMD and tissue mineral density were lower in women with DM2 than in controls. There were no differences in radius total vBMD or trabecular vBMD between groups. Despite inferior cortical bone properties at the radius, FEA-estimated failure load was similar between groups. Tibia vBMD and microarchitecture were also similar between groups. There were no significant associations between cortical parameters and duration of DM2 or HOMA-IR. However, among women with DM2, higher fasting glucose levels were associated with lower cortical vBMD (r=-0.54, p=0.018). CONCLUSIONS: DM2 and higher fasting glucose are associated with unfavorable cortical bone microarchitecture at the distal radius in African-American women. These structural deficits may contribute to the increased fracture risk among women with DM2. Further, our results suggest that hyperglycemia may be involved in mechanisms of skeletal fragility associated with DM2.

Effects of decreasing the frequency of gonadotropin-releasing hormone stimulation on gonadotropin secretion in gonadotropin-releasing hormone-deficient men and perifused rat pituitary cells.

The effects of decreasing the frequency of pulsatile gonadotropin-releasing hormone (GnRH) stimulation on pituitary responsiveness were studied in (a) men with isolated GnRH deficiency who had achieved normal sex steroid levels during prior long-term pulsatile GnRH replacement and (b) perifused dispersed pituitary cells from male rats in the absence of sex steroids. In three groups of four GnRH-deficient men, the frequency of GnRH stimulation was decreased at weekly intervals from (a) every 2-3-4 h (group I), (b) every 2-8 h without testosterone replacement (group II), or (c) every 2-8 h with testosterone replacement (group III). In three groups of three columns of perifused dispersed pituitary cells, pulses of GnRH were administered every 2, 4, or 8 h. In groups I and II, mean area under the luteinizing hormone (LH) curve increased (P less than 0.025) and serum testosterone levels fell (P less than 0.035) as the frequency of GnRH stimulation was decreased. In group III, the area under the LH curve also increased (P less than 0.01) although serum testosterone levels were constant, thereby demonstrating that the increase in pituitary responsiveness to slow frequencies of GnRH stimulation occurs independently of changes in the sex steroid hormonal milieu. The area under the LH curve also increased in the perifused dispersed rat pituitary cells when the frequency of GnRH administration was decreased to every 8 h (P less than 0.05), thus demonstrating that the enhanced pituitary responsiveness to slow frequencies of GnRH stimulation is maintained even in the complete absence of gonadal steroids. Nadir LH levels fell in all three groups (P less than 0.01) as the frequency of GnRH stimulation was decreased. In contrast, mean peak LH levels, the rate of LH rise, and the rate of endogenous LH decay were constant as the frequency of GnRH stimulation was decreased. Finally, as the GnRH interpulse interval increased, mean LH levels fell, and mean follicle-stimulating hormone levels were stable or fell. These results indicate that (a) pituitary responsiveness to GnRH increases at slower frequencies of GnRH stimulation in models both in vivo and in vitro, (b) these changes in pituitary responsiveness occur independently of changes in gonadal steroid secretion, and (c) the increases in LH pulse amplitude and area under the curve at slow frequencies of GnRH stimulation are due to decreases in nadir, but not peak, LH levels. Slowing of the frequency of GnRH secretion may be an important independent variable in the control of pituitary gonadotropin secretion.

Posterior-anterior and lateral dual-energy x-ray absorptiometry for the assessment of vertebral osteoporosis and bone loss among older men.

Lateral spine dual-energy x-ray absorptiometry (DXA) selectively measures the trabecular-rich vertebral bodies without the contributions of the cortical-rich posterior elements of the spine and is less affected by spinal degenerative disease than posterior-anterior DXA. We tested whether lateral DXA detects vertebral osteoporosis more often and is more sensitive to age-related bone loss than posterior-anterior DXA in 193 healthy, community-dwelling men aged 51-81 years (mean +/- SD; 67 +/- 8 years). All men had supine lateral, posterior-anterior, and proximal femur DXA scans on a Hologic QDR 2000 densitometer. A subset (n = 102) had repeat scans after 4 years to determine annualized rates of change in bone mineral density (BMD). Age was inversely and significantly associated with BMD in the midlateral (r = -0.27) and lateral (r = -0.24) but not posterior-anterior (r = 0.04) projections. Midlateral (-1.43 +/- 3.48% per year; p = 0.0001), lateral (-0.27 +/- 1.68% per year; p = 0.12), and hip (-0.19 +/- 1.02% per year; p = 0.06) BMD decreased, whereas posterior-anterior BMD increased (0.73 +/- 1.11% per year; p = 0.0001) during follow-up. When compared with normal values in 43 men aged 21-42 years, mean T scores were significantly lower with lateral (-1.47 +/- 1.32) and midlateral (-1.57 +/- 1.36) than posterior-anterior (-0.12 +/- 1.30; p < 0.0001) DXA. Only 2.6% of the older men were considered osteoporotic (T score < or = -2.5) at the posterior-anterior spine, whereas 11.0% were osteoporotic at the femoral neck, 22.5% at the lateral spine, and 24.6% were osteoporotic at the midlateral spine. We conclude that supine lateral DXA identifies considerably more men as osteoporotic and is more sensitive to age-related bone loss than posterior-anterior DXA. Spinal osteoporosis may represent a substantially greater health problem among older men than previously recognized.

Comparison of four methods for cross-calibrating dual-energy X-ray absorptiometers to eliminate systematic errors when upgrading equipment.

Dual-energy x-ray absorptiometry (DXA) is a widely employed technique for making noninvasive measurements of bone mineral density (BMD). Advances in DXA technology have resulted in the development of new densitometers that offer increased scan speed, improved spatial resolution, and the ability to make measurements at additional skeletal sites. However, changing from a first to a second-generation DXA system generates two additional potential sources of error. First, if the densitometers produce results that are substantially different, diagnostic errors occur if the results from both instruments are compared to the same normative database. Second, even if the densitometers produce results that are nearly identical, small systematic errors may influence interpretation of serial bone density measurements in individual patients. To assess the impact of changing from a first- to a second-generation DXA scanner, we made measurements using the standard "pencil beam" mode on 133 consecutive patients using both a Hologic QDR-1000 and a QDR-2000 densitometer when the latter instrument was calibrated according to the manufacturer's routine procedure using a single anthropomorphic spine phantom. We then recalculated the results for the QDR-2000 densitometer using cross-calibration factors based on (1) a regression line generated by scanning three anthropomorphic spine phantoms whose BMD ranged from osteoporotic to high normal on each instrument, (2) an adult human lumbar spine embedded in tissue-equivalent plastic, or (3) a regression line derived from scans of the first 83 patients that was then applied to the last 50 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of gonadal suppression on the regulation of parathyroid hormone and 1,25-dihydroxyvitamin D secretion in women.

Although a causal association between estrogen deficiency and bone loss has been established for many years, the mechanism by which estrogen deficiency leads to bone loss is unclear. Estrogen deficiency could induce bone loss either by a direct effect on bone cells to modify the production of bone-resorbing cytokines or by altering the production or response to calcium regulatory hormones such as PTH and 1,25-dihydroxyvitamin D. To assess the effects of ovarian hormones on calcium regulatory hormones, we evaluated the ability of calcium to suppress PTH secretion and the ability of PTH to increase serum 1,25-dihydroxyvitamin D and whole blood ionic calcium levels in women before and after GnRH analog-induced ovarian suppression. Sixteen women with endometriosis underwent i.v. infusion of calcium (1.1 mg calcium gluconate/cc in 5% dextrose) at a rate of 4 cc/kg x h (n = 7) or human PTH-(1-34) (Parathar) at a dose of 0.55 U/kg x h (n = 9) before and after 6 months of suppression of ovarian function with the GnRH analog nafarelin acetate (200 microg, intranasally, twice daily). Initial infusions were performed between days 6-10 of the menstrual cycle. Serum PTH and whole blood ionic calcium levels were measured at -20, -10, and 0 min and then every 10 min for 2 h during i.v. calcium infusions. Whole blood ionic calcium and 1,25-dihydroxyvitamin D levels were measured every 6 h for 24 h during i.v. human PTH-(1-34) infusions. Serum estradiol levels were markedly suppressed by nafarelin therapy in both groups of women. The relationship between whole blood ionic calcium and serum PTH levels was similar before and during nafarelin-induced ovarian suppression. The net change and rate of rise in serum 1,25-dihydroxyvitamin D levels in response to PTH infusion were similar before and during nafarelin therapy. Peak whole blood ionic calcium and incremental increases in ionic calcium in response to PTH were similar before and during nafarelin therapy. Our data suggest that ovarian suppression does not alter the regulation of PTH secretion in response to calcium, the ability of PTH to stimulate 1,25-dihydroxyvitamin D formation, or the skeletal sensitivity to PTH. These findings suggest that alterations in calcium regulatory hormones by estrogen deficiency are unlikely to play a major role in the pathogenesis of estrogen deficiency bone loss.

Increases in bone mineral density after discontinuation of daily human parathyroid hormone and gonadotropin-releasing hormone analog administration in women with endometriosis.

Intermittent PTH administration increases spinal bone mineral density (BMD) and prevents bone loss from the hip and total body in young women treated with a long acting GnRH analog for endometriosis. To establish whether these beneficial effects on BMD persist after PTH administration is discontinued, we remeasured BMD and biochemical markers of bone turnover in 38 women with endometriosis who had been treated with a GnRH analog alone (nafarelin acetate; 200 microg, intranasally, twice daily; n = 23; group 1) or who had received nafarelin plus human PTH-(1-34) (40 microg/day, s.c.; n = 15; group 2) for 6-12 months 1 yr after therapy was completed. Cyclic menstrual function returned promptly after nafarelin therapy was discontinued. In group 1, BMD increased significantly at all sites [P < 0.001 for the anterior-posterior (AP) and lateral spine; P = 0.014 for the femoral neck; P = 0.004 for the trochanter], except the proximal radius (P = 0.065) and total body bone density (P = 0.069) after nafarelin therapy was stopped. In group 2, BMD increased significantly at the AP spine (P < 0.001), lateral spine (P = 0.012), femoral neck (P = 0.002), and trochanter (P = 0.029) after nafarelin therapy was stopped. BMD of the spine in the AP projection increased more in group 2 and than in group 1 after therapy was stopped (P = 0.045). Despite these increases after discontinuation of nafarelin therapy, BMD was still significantly below baseline values at the AP spine (P < 0.001) and femoral neck (P = 0.006) and tended to be lower than baseline values at the trochanter (P = 0.057) and total body (P = 0.101) at the end of the 1-yr follow-up period in group 1. In contrast, BMD was significantly above baseline values at the AP and lateral spine (P < 0.001) sites and was similar to baseline values at the other skeletal sites at the end of the 1-yr follow-up period in group 2. Bone turnover returned to baseline values in both groups when therapy was stopped. We conclude that the beneficial effects of PTH on bone persist in women who regain cyclic menstrual function. Although part of the increases in BMD are probably due to restoration of ovarian function, additional increases in BMD most likely represent a further anabolic effect of PTH on bone that is not detected until after PTH administration is stopped.

A longitudinal evaluation of bone mineral density in adult men with histories of delayed puberty.

We have previously demonstrated that men with histories of constitutionally delayed puberty have significantly lower spinal and radial bone mineral density than normal men. Because these men were in their mid-twenties, it is possible that bone density was decreased because bone development was still incomplete. In addition, there is no information on the bone density of the proximal femur, the most important clinical site for osteoporotic fractures, in men with histories of delayed puberty. To address these issues, we performed repeat measurements of radial and spinal bone mineral density 2 yr after the initial evaluations in 18 men with histories of delayed puberty. Bone mineral density of the femoral neck was also measured at the time of follow-up evaluations. The mean radial bone mineral density at the time of the repeat evaluations was similar to the mean value from the initial evaluations (0.74 +/- 0.08 vs. 0.74 +/- 0.07 g/em2) and the mean change was 0.00 +/- 0.04 g/cm2. Similarly, the mean spinal bone mineral density at the time of the repeat evaluations was similar to the mean value from the initial evaluations (1.02 +/- 0.10 vs. 1.01 +/- 0.10 g/cm2) and the mean change was -0.01 +/- 0.04 g/cm2. Bone mineral density of the femoral neck was significantly lower in the men with histories of delayed puberty than in normal men (0.88 +/- 0.11 vs. 0.98 +/- 0.14 g/cm2 P < 0.02). These data indicate that bone accretion is complete by the mid-twenties in men with histories of constitutionally delayed puberty and that their bone mineral density does not improve with time. In addition, these men have decreased bone density of the femoral neck, which might increase their risk for hip fractures when they are older.

Osteopenia in eugonadal men with acquired immune deficiency syndrome wasting syndrome.

Multiple endocrine and metabolic consequences of human immunodeficiency virus (HIV) infection exist that may contribute to bone loss in men with the acquired immune deficiency syndrome (AIDS) wasting syndrome. Recent studies suggest that anabolic strategies can increase lean body mass in men with AIDS wasting. Prior studies have not examined the effects of anabolic agents on bone mineral density (BMD) or bone turnover in these men. To determine the effects of testosterone and progressive resistance training on BMD and bone turnover in eugonadal men with AIDS wasting, we randomly assigned 54 eugonadal men with AIDS wasting (weight < 90% IBW or weight loss >10% from preillness baseline) to receive either testosterone enanthate (200 mg/week, im) or placebo and to progressive resistance training (3 times/week) or no training in a 2 x 2 factorial study design for 3 months. The BMD of the lumbar spine, proximal femur, and total body; lean body mass; and fat mass were measured by dual energy x-ray absorptiometry. Total body scans were repeated after 12 weeks of therapy. Baseline bone turnover and BMD were compared with those in 35 age-matched healthy non-HIV-infected control subjects. Compared with controls, lumbar spine BMD (1.021 +/- 0.018 vs. 1.084 +/- 0.025 g/cm(2); P = 0.04) and total hip BMD (0.951 +/- 0.017 vs. 1.070 +/- 0.019 g/cm(2); P < 0.0001) were reduced in men with AIDS wasting. T-scores were lower in men with AIDS wasting at the lumbar spine (-0.62 +/- 0.17 vs. -0.07 +/- 0.23, P = 0.05) and total hip (-0.65 +/- 0.11 vs. +0.20 +/- 0.014, P < 0.0001). Total hip T scores were less than -1.0 in 33% of men with AIDS wasting. Neither the use of protease inhibitors nor the duration of protease inhibitors use correlated with BMD. Serum osteocalcin levels were lower (3.63 +/- 0.29 vs. 4.54 +/- 0.31 nmol/L; P < 0.04) and urinary N-telopeptide excretion was higher (45.4 +/- 4.5 vs. 26.8 +/- 3.0 nmol BCE/mmol creatinine; P = 0.004) in men with AIDS wasting than in controls. Lumbar spine BMD, as assessed on regional total body dual energy x-ray absorptiometry scan, increased over the 12-week treatment period in response to testosterone (+2.4 +/- 1.3 vs. -1.3 +/- 1.0%, testosterone vs. placebo, respectively; P = 0.02), but not in response to training (+0.8 +/- 1.0 vs. +0.4 +/- 1.3%, training vs. no training; P = 0.70). Lumbar spine and total hip BMD are reduced in eugonadal men with AIDS wasting. Biochemical markers of bone turnover suggest that bone formation and bone resorption are uncoupled in these men. Testosterone administration, but not resistance training, over 3 months increases lumbar spine BMD in eugonadal men with AIDS wasting.

Effects of gonadal steroid suppression on skeletal sensitivity to parathyroid hormone in men.

Hypogonadism is associated with osteoporosis in men. GnRH- agonist-induced hypogonadism increases bone turnover and bone loss in men, but the mechanism underlying these changes is unknown. To determine whether gonadal steroid deprivation increases the skeletal sensitivity to PTH or blunts the ability of PTH to promote 1,25-dihydroxyvitamin D formation, we infused human PTH-(1-34) at a dose of 0.55 U/kg.h for 24 h, in 11 men (ages, 50-82 yr) with locally advanced, node-positive, or biochemically recurrent prostate cancer but no evidence of bone metastases. PTH infusions were performed before initiation of GnRH agonist therapy (leuprolide acetate, 22.5 mg im, every 3 months) and again after 6 months of confirmed GnRH agonist-induced hypogonadism. Serum osteocalcin (OC), bone- specific alkaline phosphatase (BSAP), N-telopeptide (NTX), whole-blood ionized calcium, and 1,25-dihydroxyvitamin D were measured at baseline and every 6 h during each PTH infusion. Urinary NTX and free deoxypyridinoline (DPD) were assessed on spot morning samples before PTH infusion and on 24-h samples collected during the PTH infusions. Sex steroid levels were lowered to the castrate range in all subjects. Baseline serum NTX levels (drawn before PTH infusion) increased from 9.1 +/- 3.7 before leuprolide therapy to 13.9 +/- 5.0 nmol bone collagen equivalents (BCE)/L after leuprolide therapy (P = 0.003). Spot urine NTX collected before PTH infusion increased from 28 +/- 8 before leuprolide therapy to 49 +/- 17 nmol BCE/mmol creatinine after leuprolide therapy (P < 0.001), and urinary DPD increased from 4.7 +/- 1.1 to 7.4 +/- 1.8 nmol BCE/mmol creatinine (P < 0.001). Baseline serum OC and BSAP levels drawn before each PTH infusion did not change before vs. after leuprolide therapy. Serum NTX levels increased significantly during PTH infusion pre-GnRH agonist therapy (P < 0.001), and the rate of increase was greater after 6 months of GnRH agonist-induced hypogonadism (P < 0.01 for the difference in rates of change before and after GnRH agonist administration). Serum OC and BSAP levels decreased during PTH infusion (P < 0.001 for OC and P = 0.002 for BSAP), but the rates of decrease did not differ before or after leuprolide therapy (P = 0.45 for OC and P: = 0.19 for BSAP). Whole-blood ionized calcium levels increased during PTH infusion (P < 0.001), and the rate of increase was greater after GnRH agonist-induced hypogonadism (P = 0.068). Serum 1,25-dihydroxyvitamin D levels increased in response to PTH infusion before leuprolide therapy (P = 0.022), but there was no difference in the rate of increase before or after leuprolide therapy (P = 0.66). The incremental increase in urinary NTX excretion, but not DPD, during PTH infusion was greater after 6 months of leuprolide therapy (P = 0.029 for NTX, P = 0.578 for DPD). We conclude that suppression of sex steroids in elderly men increases the skeletal responsiveness to the bone resorbing effects of PTH infusion but does not affect the response of bone formation markers or 1,25-dihydroxyvitamin D to PTH. Changes in skeletal sensitivity to PTH may play an important role in the pathogenesis of hypogonadal bone loss in men.

Sex steroid control of gonadotropin secretion in the human male. II. Effects of estradiol administration in normal and gonadotropin-releasing hormone-deficient men.

Although prior studies have suggested that estrogens exert their negative feedback effect at the pituitary level in men, these conclusions have been based on models that evaluate changes in LH pulse amplitude and frequency and, therefore, only provide indirect information concerning the site of action of estrogens. To assess whether estradiol (E2) inhibits gonadotropin secretion directly and solely at the pituitary level in men, we determined the pituitary responses to physiological doses of GnRH in six men with complete GnRH deficiency, whose pituitary-gonadal function had been normalized with long term pulsatile GnRH delivery, before and during a 4-day continuous E2 infusion (90 micrograms/day). To deduce whether E2 has an additional inhibitory effect on hypothalamic GnRH secretion, their responses were compared with the effects of identical E2 infusions on spontaneous gonadotropin secretion and the responses to a 100-micrograms GnRH bolus in six normal men. Both groups were monitored with 15 h of frequent blood sampling before and during the last day of the E2 infusion. In the GnRH-deficient men, the first three GnRH doses were identical and chosen to produce LH pulses with amplitudes in the midphysiological range of values in our normal men (i.e. a physiological dose), while the last four doses spanned 1.5 log orders (7.5, 25, 75, and 250 ng/kg). The 250-ng/kg dose was always administered last because it is known to be pharmacological. In the GnRH-deficient men, mean LH and FSH levels as well as LH pulse amplitude all decreased significantly (P less than 0.02) during E2 infusion, demonstrating a direct pituitary-suppressive effect of E2. Mean LH (P less than 0.01) and FSH (P less than 0.05) levels and LH pulse amplitude (P less than 0.01) also decreased significantly in the normal men. The degree of suppression of mean LH (52 +/- 3% vs. 42 +/- 12%) and FSH (49 +/- 10% vs. 37 +/- 10%) levels was similar in the two groups. These results provide direct evidence that E2 inhibits gonadotropin secretion at the pituitary level in men and suggest that the pituitary is the most important, and possibly the sole, site of negative feedback of estrogens in men.

Bio- and immunoactive luteinizing hormone responses to low doses of gonadotropin-releasing hormone (GnRH): dose-response curves in GnRH-deficient men.

Previous investigations of the effects of GnRH on pituitary LH responses in normal men required pharmacological doses of GnRH to avoid the confounding effects of endogenous GnRH secretion and employed nonphysiological dose intervals. To examine the role of GnRH in determining both the qualitative and quantitative nature of physiological LH responses, we studied five GnRH-deficient men in whom pituitary and gonadal function had been normalized with GnRH replacement. Both bio- and immunoactive LH responses were evaluated in these men after a wide range of GnRH doses (7.5-250 ng/kg) administered at a physiological frequency (every 2 h), while gonadal steroid levels were within the normal adult male range. In addition, the amplitude and contour of the immunoactive LH pulses were compared to those of 15 normal men to assure that these experiments achieved physiological pituitary responses. The relationship between bio- and immunoactive LH was compared between patients, between doses as the amount of GnRH was increased, and within pulses of LH. As the dose of GnRH was increased, both bio- and immunoactive LH responses increased in a log-linear fashion when assessed by both amplitude (r = 0.96 for bioactive LH and r = 0.98 for immunoactive LH) and area under the curve (r = 0.99 for bioactive LH and r = 0.97 for immunoactive LH). GnRH doses of 7.5 and 25 ng/kg produced LH responses with amplitudes similar to those in normal men. The relationship between bio- and immunoactive LH between patients and between differing doses of GnRH was analyzed by comparing the slopes of lines fit to individual bioactive vs. immunoactive LH plots after each dose of GnRH in each patient. There was a marked variation in the relationship of bio- to immunoactive LH between patients (P less than 0.005). No change was found in the biopotency of LH as the dose of GnRH was increased (P less than 0.10). Finally, no variation of the bioactivity of LH was evident within individual pulses. We conclude that a log-linear relationship exists between doses of GnRH that produce physiological LH pulses and both bio- and immunoactive LH responses; the bioactivity of secreted LH varies markedly between patients; the relative bioactivity of LH in an individual does not change as the dose of GnRH is increased; and no change in bioactivity of LH responses was demonstrated within pulses of LH.

Effects of increasing the frequency of low doses of gonadotropin-releasing hormone (GnRH) on gonadotropin secretion in GnRH-deficient men.

The effects of increasing the frequency of pulsatile GnRH administration on LH and FSH responsiveness were studied in five GnRH-deficient men who had achieved normal sex steroid levels during prior long term GnRH replacement. Intravenous doses of GnRH were employed that had previously been demonstrated to produce LH and FSH levels in each subject similar to those in normal men. Both acute and chronic changes in pituitary responses were studied after progressive increases in GnRH frequency (from every 120 to 60 min, from 60 to 30 min, and from 30 to 15 min) during three 12-h admissions, each separated by 7 days. During the two intervals between the studies GnRH frequency was 60 and 30 min, respectively. Pituitary responses were characterized by determining the mean serum LH and FSH levels, LH pulse amplitudes, and mean LH and FSH levels which were normalized for the frequency of GnRH administration (nLH and nFSH). As the frequency of GnRH stimulation was increased acutely, mean serum LH levels rose progressively, in contrast to both LH pulse amplitude and nLH levels which decreased, while serum testosterone (T) concentrations remained constant. No further evidence of gonadotroph desensitization occurred after chronic GnRH administration at either 60- or 30-min intervals. At higher frequencies of GnRH stimulation, discrete pulses of LH were not always apparent after injections of GnRH, and in two men, marked destabilization of the gonadotroph responses occurred. Even without detectable LH pulses, serum T levels did not decline during administration of GnRH at intervals as rapid as 15 min. In contrast, there was no change in mean FSH concentrations, although nFSH values decreased progressively as the GnRH frequency was increased. nFSH levels fell to a greater degree than nLH after each increase in GnRH frequency. Thus, pituitary gonadotroph responsiveness to a fixed dose of GnRH decreased as the frequency of GnRH stimulation increased. FSH responsiveness decreased to a greater degree than did LH. Gonadotropin secretory responses are destabilized at higher frequencies of GnRH administration. Pulsatile LH stimulation of the testes does not appear necessary to maintain T secretion.

Increase in bone density and lean body mass during testosterone administration in men with acquired hypogonadism.

Acquired hypogonadism is being increasingly recognized in adult men. However, the effects of long term testosterone replacement on bone density and body composition are largely unknown. We investigated 36 adult men with acquired hypogonadism (age, 22-69 yr; median, 58 yr), including 29 men with central hypogonadism and 7 men with primary hypogonadism, and 44 age-matched eugonadal controls. Baseline evaluation included body composition analysis by bioimpedance, determination of site-specific adipose area by dual energy quantitative computed tomography scan (QCT) of the lumbar spine, and measurements of spinal bone mineral density (BMD) using dual energy x-ray absortiometry, spinal trabecular BMD with QCT, and radial BMD with single photon absorptiometry. Percent body fat was significantly greater in the hypogonadal men compared to eugonadal men (mean +/- SEM, 26.4 +/- 1.1% vs. 19.2 +/- 0.8%; P < 0.01). The mean trabecular BMD determined by QCT for the hypogonadal men was 115 +/- 6 mg K2HPO4/cc. Spinal BMD was significantly lower than that in eugonadal controls (1.006 +/- 0.024 vs. 1.109 +/- 0.028 g/cm2; P = 0.02, respectively). Radial BMD was similar in both groups. Testosterone enanthate therapy was initiated in 29 hypogonadal men at a dose of 100 mg/week, and the subjects were evaluated at 6-month intervals for 18 months. During testosterone therapy, the percent body fat decreased 14 +/- 4% (P < 0.001). There was a 13 +/- 4% decrease in subcutaneous fat (P < 0.01) and a 7 +/- 2% increase in lean muscle mass (P = 0.01) during testosterone therapy. Spinal BMD and trabecular BMD increased by 5 +/- 1% (P < 0.001) and 14 +/- 3% (P < 0.001), respectively. Radial BMD did not change. Serum bone-specific alkaline phosphatase and urinary deoxypyridinoline excretion, markers of bone formation and resorption, respectively, decreased significantly over the 18 months (P = 0.003 and P = 0.04, respectively). We conclude that testosterone therapy given to adult men with acquired hypogonadism decreases sc fat and increases lean muscle mass. In addition, testosterone therapy reduces bone remodeling and increases trabecular bone density. The beneficial effects of androgen administration on body composition and bone density may provide additional indications for testosterone therapy in hypogonadal men.

Metabolism of orally administered androstenedione in young men.

Androstenedione is a steroid hormone and the major precursor to testosterone. It is available without prescription and taken with the expectation that it will be converted to testosterone endogenously and increase strength and athletic performance. The metabolism of orally administered testosterone has not been well studied. We randomly assigned 37 healthy men to receive 0, 100, or 300 mg oral androstenedione in a single daily dose for 7 d. Single 8-h urine collections were performed on the day before the start of the androstenedione administration and on d 1 and 7 to assess excretion rates of free and glucuronide- conjugated testosterone, androsterone, etiocholanolone, and dihydrotestosterone. Serum testosterone glucuronide concentrations were measured by frequent blood sampling over 8 h on d 1 in 16 subjects (5 each in the 0 and 100 mg group and 6 in the 300 mg group). In the control group, mean (+/-SE) d 1 and 7 excretion rates for testosterone, androsterone, etiocholanolone, and dihydrotestosterone were 3 +/- 1, 215 +/- 26, 175 +/- 26, and 0.4 +/- 0.1 microg/h, respectively. In the 100 mg group, mean d 1 and 7 excretion rates for testosterone, androsterone, etiocholanolone, and dihydrotestosterone were 47 +/- 11, 3,836 +/- 458, 4,306 +/- 458, and 1.6 +/- 0.2 microg/h, respectively. In the 300 mg group, mean d 1 and 7 excretion rates for testosterone, androsterone, etiocholanolone, and dihydrotestosterone were 115 +/- 39, 8,142 +/- 1,362, 10,070 +/- 1,999, and 7.7 +/- 1.5 microg/h, respectively. Urinary excretion rates of all metabolites were greater in both the 100 and 300 mg groups than in controls (P < 0.0001). Urinary excretion rates of testosterone (P = 0.007), androsterone (P = 0.009), etiocholanolone (P = 0.0005), and dihydrotestosterone (P < 0.0001) were greater in the subjects who received 300 mg androstenedione than in those who received 100 mg. In the treated groups, excretion of free testosterone accounted for less than 0.1% of the total excreted testosterone measured. Serum testosterone glucuronide levels increased significantly during frequent blood sampling in both the 100 and 300 mg groups compared with controls (P = 0.0005 for the 100 mg group; P < 0.0001 for the 300 mg group). The net mean changes in area under the curve for serum testosterone glucuronide were -18 +/- 25%, 579 +/- 572%, and 1267 +/- 1675% in the groups receiving 0, 100, and 300 mg/d androstenedione, respectively. We conclude that the administration of both 100 and 300 mg androstenedione increases the excretion rates of conjugated testosterone, androsterone, etiocholanolone, and dihydrotestosterone and the serum levels of testosterone glucuronide in men. The magnitude of these increases is much greater than the changes observed in serum total testosterone concentrations. These findings demonstrate that orally administered androstenedione is largely metabolized to testosterone glucuronide and other androgen metabolites before release into the general circulation.

Utility of free alpha-subunit as an alternative neuroendocrine marker of gonadotropin-releasing hormone (GnRH) stimulation of the gonadotroph in the human: evidence from normal and GnRH-deficient men.

To examine the hypothesis that the secretion of free alpha-subunit (FAS) can serve as an alternative to LH as a neuroendocrine marker of gonadotroph stimulation by GnRH in euthyroid humans, we have investigated the relationship of pulsatile FAS secretion in euthyroid GnRH-deficient men (n = 10) before and after exogenous GnRH stimulation and in normal men under the influence of endogenous GnRH secretion (n = 18). Before GnRH exposure, the GnRH-deficient men showed a complete absence of both LH and FAS pulses. During the initial 7 days of GnRH exposure, all GnRH-deficient men exhibited pulsatile release of FAS by the third day, whereas the appearance of pulsatile release of LH and FSH was more variable. Long term administration of GnRH led to pulses of LH and FAS that were 100% concordant with a demonstrable dose-response relationship between GnRH and FAS, which was quantitatively similar to but more exuberant than that for LH. All doses of GnRH that produced LH pulses within the normal adult range yielded supraphysiological FAS pulses. Analysis of distribution histograms of interpulse intervals and pulse amplitudes of LH and FAS in both normal and GnRH-deficient subjects demonstrated no significant difference between these glycoproteins in interpulse intervals in either the normal or GnRH-deficient groups or in the pulse amplitudes in the GnRH-deficient subjects. There was, however, a significant difference (P less than 0.01) between the distribution histogram of LH and FAS pulse amplitudes in normal men. We conclude that the pulsatile secretion of FAS in euthyroid men 1) is determined by GnRH secretion, 2) is the initial glycoprotein to be secreted in a pulsatile fashion from the gonadotroph during early GnRH exposure in GnRH-deficient men, 3) demonstrates a dose-response relationship to exogenous GnRH which is more robust than that of LH in GnRH-deficient men receiving GnRH, and 4) can, therefore, serve as a complementary and powerful tool with LH for the study of GnRH neurosecretory dynamics.

Sex steroid control of gonadotropin secretion in the human male. I. Effects of testosterone administration in normal and gonadotropin-releasing hormone-deficient men.

The precise sites of action of the negative feed-back effects of gonadal steroids in men remain unclear. To determine whether testosterone (T) administration can suppress gonadotropin secretion directly at the level of the pituitary, the pituitary responses to physiological doses of GnRH were assessed in six men with complete GnRH deficiency, whose pituitary-gonadal function had been normalized with long term pulsatile GnRH delivery, before and during a 4-day continuous T infusion (15 mg/day). Their responses were compared with the effects of identical T infusions on spontaneous gonadotropin secretion and the response to a 100-micrograms GnRH bolus in six normal men. Both groups were monitored with 15 h of frequent blood sampling before and during the last day of the T infusion. In the GnRH-deficient men, the first three GnRH doses were identical and were chosen to produce LH pulses with amplitudes in the midphysiological range of our normal men (i.e. a physiological dose), while the last four doses spanned 1.5 log orders (7.5, 25, 75, and 250 ng/kg). The 250 ng/kg dose was always administered last because it is known to be pharmacological. In the GnRH-deficient men, mean LH (P less than 0.02) and FSH (P less than 0.01) levels as well as LH pulse amplitude (P less than 0.05) decreased significantly during T infusion, demonstrating a direct pituitary-suppressive effect of T and/or its metabolites. Mean LH levels were suppressed to a greater extent in the normal than in the GnRH-deficient men (58 +/- 15% vs. 28 +/- 7%; P less than 0.05). In addition, LH frequency decreased significantly (P less than 0.01) during T administration in the normal men. These latter two findings suggest that T administration also suppresses hypothalamic GnRH release. T was unable to suppress gonadotropin secretion in one GnRH-deficient and one normal man. In both groups, the suppressive effect of T administration was present only in response to physiological doses of GnRH. Because the pituitary- and hypothalamus-suppressive effects of T could be mediated by its aromatization to estrogens, five GnRH-deficient and five normal men underwent identical T infusions with concomitant administration of the aromatase inhibitor testolactone (TL; 500 mg, orally, every 6 h). As an additional control, four GnRH-deficient and four normal men received TL alone. TL administration completely prevented the effect of T administration to suppress gonadotropin secretion in both the normal and GnRH-deficient men, and mean LH levels increased significantly in both the GnRH-deficient (P less than 0.01) and the normal (P less than 0.001) men who received TL alone. The increase in mean LH levels was greater (P less than 0.01) in the normal men who received TL alone than in the normal men who received T plus TL, thus revealing a direct effect of androgens in normal men. Measurements of T and estradiol production rates in three men demonstrated that TL effectively blocked aromatization.(ABSTRACT TRUNCATED AT 400 WORDS)

Pulsatile gonadotropin secretion after discontinuation of long term gonadotropin-releasing hormone (GnRH) administration in a subset of GnRH-deficient men.

Normal pituitary and gonadal function can be maintained with long term pulsatile GnRH administration in men with idiopathic hypogonadotropic hypogonadism (IHH), and both pituitary and gonadal priming occur during the process of GnRH-induced sexual maturation. Still, the long term effects of discontinuing GnRH therapy in IHH men have not been examined. Therefore, we evaluated the patterns of gonadotropin and alpha-subunit secretion before and after a prolonged period of pulsatile GnRH administration in 10 IHH men. Before exogenous GnRH stimulation, no patient had any detectable LH pulsations. In 6 of these men, who were typical of most of our IHH patients (group I), no LH pulsations were detectable after cessation of GnRH administration. However, in the other 4 men (group II), LH pulsations were easily detectable despite cessation of exogenous GnRH stimulation, and the amplitude (9.3 +/- 3.5 IU/L) and frequency (13.8 +/- 1.7 pulses/day) of these LH pulses were similar to those in 20 normal men (10.6 +/- 0.7 IU/L and 11.0 +/- 0.7 pulses/day). Three of these 4 men in group II maintained normal serum testosterone levels after discontinuation of GnRH delivery. To determine if there were any characteristics that might be useful in predicting which IHH men could maintain normal pituitary-gonadal function after long term GnRH administration, we evaluated various clinical and hormonal parameters at the time of initial presentation. Mean alpha-subunit levels (P less than 0.01) and alpha-subunit pulse amplitude (P less than 0.02) were significantly higher in the group II than the group I men, suggesting that the group II patients had partial, rather than complete, deficiency of endogenous GnRH secretion. None of the other parameters that were assessed distinguished the two groups. We conclude that gonadotropin and sex steroid levels return to their pretreatment state in the majority of IHH men when long term GnRH administration is discontinued. Normal pituitary-gonadal function can be maintained after discontinuation of long term GnRH administration in a rare subset of IHH men who present with higher levels of alpha-subunit. We hypothesize that these latter IHH men have an incomplete GnRH deficiency and that long term exogenous GnRH administration induces pituitary and gonadal priming, which subsequently enables them to sustain normal pituitary and gonadal function in response to their own enfeebled GnRH secretion.

Increases in bone density during treatment of men with idiopathic hypogonadotropic hypogonadism.

To assess the effects of gonadal steroid replacement on bone density in men with osteoporosis due to severe hypogonadism, we measured cortical bone density in the distal radius by 125I photon absorptiometry and trabecular bone density in the lumbar spine by quantitative computed tomography in 21 men with isolated GnRH deficiency while serum testosterone levels were maintained in the normal adult male range for 12-31 months (mean +/- SE, 23.7 +/- 1.1). In men who initially had fused epiphyses (n = 15), cortical bone density increased from 0.71 +/- 0.02 to 0.74 +/- 0.01 g/cm2 (P less than 0.01), while trabecular bone density did not change (116 +/- 9 compared with 119 +/- 7 mg/cm3). In men who initially had open epiphyses (n = 6), cortical bone density increased from 0.62 +/- 0.01 to 0.70 +/- 0.03 g/cm2 (P less than 0.01), while trabecular bone density increased from 96 +/- 13 to 109 +/- 12 mg/cm3 (P less than 0.01). Cortical bone density increased 0.03 +/- 0.01 g/cm2 in men with fused epiphyses and 0.08 +/- 0.02 g/cm2 in men with open epiphyses (P less than 0.05). Despite these increases, neither cortical nor trabecular bone density returned to normal levels. Histomorphometric analyses of iliac crest bone biopsies demonstrated that most of the men had low turnover osteoporosis, although some men had normal to high turnover osteoporosis. We conclude that bone density increases during gonadal steroid replacement of GnRH-deficient men, particularly in men who are skeletally immature.