Macimorelin (AEZS-130)-stimulated growth hormone (GH) test: validation of a novel oral stimulation test for the diagnosis of adult GH deficiency.

CONTEXT: In the absence of panhypopituitarism and low serum IGF-I levels, the diagnosis of adult GH deficiency (AGHD) requires confirmation with a GH stimulation test. Macimorelin is a novel, orally active ghrelin mimetic that stimulates GH secretion. OBJECTIVE: The objective of the study was to determine the diagnostic efficacy and safety of macimorelin in AGHD. DESIGN: This was a multicenter open-label study comparing the diagnostic accuracy of oral macimorelin with that of arginine+GHRH in AGHD patients and healthy, matched controls. After 43 AGHD patients and 10 controls were tested, the GHRH analog Geref Diagnostic [GHRH(1-29)NH2] became unavailable in the United States. The study was completed by testing 10 additional AGHD patients and 38 controls with macimorelin alone. MAIN OUTCOME MEASURE: Peak GH area under the receiver operating characteristic curve after macimorelin was measured. RESULTS: Fifty AGHD subjects and 48 controls were evaluated. Peak GH levels in AGHD patients and controls after macimorelin were 2.36 ± 5.69 and 17.71 ± 19.11 ng/mL, respectively (P < .0001). With macimorelin, the receiver operating characteristic analysis yielded an optimal GH cut point of 2.7 ng/mL, with 82% sensitivity, 92% specificity, and 13% misclassification rate. For subjects receiving both tests, macimorelin showed discrimination comparable with arginine+GHRH (area under the receiver operating characteristic curve 0.99 vs 0.94, respectively, P = .29). Obesity (body mass index > 30 kg/m(2)) was present in 58% of subjects, and peak GH levels were inversely associated with body mass index in controls (r = -0.37, P = .01). Using the separate cut points of 6.8 ng/mL for nonobese and 2.7 for obese subjects reduced the misclassification rate to 11%. Only 1 drug-related serious adverse event, an asymptomatic QT interval prolongation on the electrocardiogram, was reported. CONCLUSION: Oral macimorelin is safe, convenient, and effective in diagnosing AGHD with accuracy comparable with the arginine+GHRH test.

Using basic science to design a clinical trial: baseline characteristics of women enrolled in the Kronos Early Estrogen Prevention Study (KEEPS).

Observational and epidemiological studies suggest that menopausal hormone therapy (MHT) reduces cardiovascular disease (CVD) risk. However, results from prospective trials showed neutral or adverse effects most likely due to differences in participant demographics, such as age, timing of initiation of treatment, and preexisting cardiovascular disease, which reflected in part the lack of basic science information on mechanisms of action of hormones on the vasculature at the time clinical trials were designed. The Kronos Early Estrogen Replacement Study (KEEPS) is a prospective, randomized, controlled trial designed, using findings from basic science studies, to test the hypothesis that MHT when initiated early in menopause reduces progression of atherosclerosis. KEEPS participants are younger, healthier, and within 3 years of menopause thus matching more closely demographics of women in prior observational and epidemiological studies than women in the Women's Health Initiative hormone trials. KEEPS will provide information relevant to the critical timing hypothesis for MHT use in reducing risk for CVD.

KEEPS: The Kronos Early Estrogen Prevention Study.

Observational studies have indicated that hormone therapy given at or after menopause is linked to substantial reduction in cardiovascular disease and its risk factors. Recent findings from the Women's Health Initiative (WHI) clinical trial, however, indicate that combined estrogen plus progestin hormone therapy, as well as estrogen-alone hormone therapy (given to women without a uterus), is ineffective in preventing the new onset of cardiac events in previously healthy late menopausal women. Further, the secondary prevention trial, the Heart and Estrogen/progestin Replacement Study (HERS), also failed to demonstrate any benefit of initiation of hormone therapy in women with established coronary heart disease. In light of these results, a hypothesis has arisen that early initiation of hormone therapy, in women who are at the inception of their menopause, will delay the onset of subclinical cardiovascular disease in women. The rationale that earlier intervention than that performed in the WHI and HERS trials will provide cardiovascular benefit to women is the driving force behind the Kronos Early Estrogen Prevention Study, or KEEPS. KEEPS is a multicenter, 5-year clinical trial that will evaluate the effectiveness of 0.45 mg of conjugated equine estrogens, 50 microg weekly transdermal estradiol (both in combination with cyclic oral, micronized progesterone, 200 mg for 12 days each month), and placebo in preventing progression of carotid intimal medial thickness and the accrual of coronary calcium in women aged 42-58 years who are within 36 months of their final menstrual period. A total of 720 women are planned to be enrolled in 2005, with an anticipated close-out of the trial in 2010. This overview summarizes the recruitment and methodology of the KEEPS trial.

Neuroendocrine aging in men. Andropause and somatopause.

Aging is accompanied by gradual but progressive reductions in the secretion of testosterone and growth hormone in men, and by alterations in body composition and functional capacity that, to some degree, undo the effects of puberty. Preventing or reversing these changes with the use of trophic factors, including androgens, growth hormone, and growth hormone secretagogues, is an appealing prospect, but documenting the effectiveness of these interventions and their benefits and risks has proven to be a difficult undertaking that is far from complete. Small-scale clinical studies have shown that it is practicable to boost growth hormone and IGF-1 levels for periods of up to 12 months, and testosterone for up to 36 months, to reverse at least some age-related changes in body composition. Information regarding the effects of these interventions on strength, exercise capacity, and the ability to perform activities of daily living is still sparse, and additional reports from recently completed or currently ongoing clinical trials will not provide sufficient data to make firm conclusions. From the limited information currently available, androgen supplementation may be of benefit in some men aged more than 65 years, particularly in men with low serum testosterone levels (< 2 ng/mL). In this group, supplemental androgen therapy would be expected to increase lean body mass, bone mass, and possibly strength. In older men with testosterone levels between 2 and 3.5 ng/mL, some benefit might result from androgen supplementation, but it is not yet clear whether the benefits outweigh the risks. For men in this category, one might consider a 6- to 12-month trial of therapy after a full discussion and explicit consent, followed by a reassessment of the value of ongoing treatment. The even more limited data on growth hormone or growth hormone secretagogue interventions in aging do not support their general clinical use in healthy older men. Growth hormone is much more expensive than testosterone and is not covered by insurance for off-label uses. Patients who persistently seek a trial of therapy should be encouraged to enroll in a study if one is locally available. All of the growth hormone studies reported to date have focused, generally for reasons of safety, on healthy and robust groups of older subjects, men in whom the need for intervention is least compelling and in whom the functional effects of treatment may be the most difficult to observe. Phase II studies of intermediate size and duration examining prefrail groups of elderly who are at greater risk for functional loss and who stand to benefit the most from either preventive or restorative interventions are underway but are limited to the intermediate outcomes of body composition, strength, and function. Trials designed to assess clinically relevant final outcomes, such as falls, fractures, and institutionalization, are of necessity large-scale, long-term, and expensive. Support for larger phase III studies of growth hormone is unlikely to be forthcoming until the phase II studies are completed and show further promise. A multicenter clinical trial of testosterone is currently being planned under the joint sponsorship of the National Institute on Aging, the Veterans Health Administration, and industry, aimed at assessing the effects of testosterone on the risk for falls and fractures. The results of this trial and other large clinical trials should help to better define the balance of benefits and risks of trophic factor intervention in normal older men.

Treating age-related changes in somatotrophic hormones, sleep, and cognition.

Many of the body's systems that function to maintain optimal health and well-being decline with advancing age. Aerobic capacity, muscle mass, and strength all progressively decline. Significant sleep disturbances are associated with increases in morbidity and mortality. Cognition declines, impacting an older individual's ability to function independently. Interventions that could at least stabilize or possibly improve functional capacity, sleep quality, and cognitive function have the theoretical potential to prolong an older individual's ability to live independently, and interest in their possible utility is growing rapidly. One such intervention may be stimulation of the "somatotrophic" axis via growth hormone-releasing hormone (GHRH). Here we review the evidence for such somatotrophic interventions. We also report preliminary findings on the effects of chronic GHRH treatment on the somatotrophic hormones, body composition, functional status, sleep, and cognitive function of healthy older men and women from two major GHRH intervention studies, one recently completed and the other ongoing.

Physiology of the menstrual cycle.

The normal female life cycle is associated with a number of hormonal milestones: menarche, pregnancy, contraceptive use, menopause, and the use of replacement sex hormones. All these events and interventions alter the levels and cycling of sex hormones and may cause a change in the prevalence or intensity of headache. The menstrual cycle is the result of a carefully orchestrated sequence of interactions among the hypothalamus, pituitary, ovary, and endometrium, with the sex hormones acting as modulators and effectors at each level. Oestrogen and progestins have potent effects on central serotonergic and opioid neurons, modulating both neuronal activity and receptor density. The primary trigger of menstrual migraine appears to be the withdrawal of oestrogen rather than the maintenance of sustained high or low oestrogen levels. However, changes in the sustained oestrogen levels with pregnancy (increased) and menopause (decreased) appear to affect headaches. Headaches that occur with premenstrual syndrome appear to be centrally generated, involving the inherent rhythm of CNS neurons, including perhaps the serotonergic pain-modulating systems.

Thyroid hormones: positive relationships with cognition in healthy, euthyroid older men.

BACKGROUND: Although the association of clinical hypothyroidism with cognitive deficits is well known, the cognitive effects of thyroid hormones in euthyroid subjects are less studied and understood. The purpose of this study was to examine thyroid-cognition relationships in healthy, euthyroid older men. METHODS: We examined healthy men (N = 44, mean age = 72), excluding clinically hypothyroid/hyperthyroid or diabetic/hyperglycemic subjects and those with dementia, depression, CNS medications, or recent illness. Plasma samples obtained across a 24-hour period were pooled, then assayed for total thyroxine (TT4), total triiodothyronine (TT3), and T3 resin uptake. Free thyroxine index (FT4I) was calculated. A broad cognitive battery (including the Wechsler Adult Intelligence Scale-Revised [WAIS-R], the Dementia Rating Scale [DRS], and the Rivermead Behavioral Profile [PROFILE]) was administered to all subjects. RESULTS: Regression analyses controlling age and education showed TT4 and FT4I to have significant positive relationships with measures of overall cognition; TT4 accounted for 8% to 12% of the variance in omnibus cognitive measures such as WAIS Performance, WAIS Verbal score, and GLOBAL cognitive scores. CONCLUSIONS: Our findings suggest that within "normal" range of variation in plasma thyroid hormones, TT4 but not T3 positively associates with general cognition in healthy elderly men.

Age-related changes in growth hormone secretion: should the somatopause be treated?

Growth hormone (GH) secretion declines progressively with aging, and many age-related changes resemble those of the adult GH deficiency (GHD) syndrome, including a decrease in lean body mass; an increase in body fat, especially in the visceral/abdominal compartment; adverse changes in lipoproteins; and a reduction in aerobic capacity. The increase in central obesity can further inhibit GH secretion. GH replacement is effective in reversing many of these changes in adult GHD, and GH is now FDA approved for treatment of adults with documented GHD or hypopituitarism, although there is still only limited experience with its long-term benefits, side effects, and risks. This early experience with GHD has led to speculation that replacing GH or stimulating its secretion may also be beneficial in normal aging, and to widespread off-label use of GH in this context; however, there are still very few well controlled studies of the effects and side effects of GH or GH secretagogues in aging. All published studies are of 6 months or shorter treatment periods. From this limited experience there is a consensus that GH has effects on body composition, but reports disagree on effects on psychological or physical functional performance. Older adults are much more susceptible to the dose-related side effects of GH, including peripheral edema, carpal tunnel syndrome, and a variable decrease in insulin sensitivity; and it is not known whether chronic GH treatment affects the risk of malignancy or has other long-term risks. Thus while short-term results are somewhat encouraging, the evidence on risks and clinically pertinent benefits is still lacking to support the use of GH in normal aging outside of clinical studies. In evaluating patients with clinical features suggesting GHD, which can be quite nonspecific, it is important to assess the presence or absence of true GH deficiency by the context (pituitary disease or its treatment, childhood GHD) and by appropriate GH stimulation tests before considering GH replacement.

Effects of eight months treatment with graded doses of a growth hormone (GH)-releasing peptide in GH-deficient children.

Stimulation of pituitary GH secretion with administered GHRH can be effective therapy for those GH deficient (GHD) patients whose disorder results from insufficient endogenous GHRH secretion. We have previously shown that most such patients also respond acutely to the GH-releasing peptides (GHRP's), which have a different mechanism of action from GHRH, with release of GH. In this study we tested whether the GH response to a newer GHRP, GHRP-2, would be sustained over time. Six prepubertal children with GHD and growth failure received stepwise increasing s.c. doses of GHRP-2, at 0.3, 1.0, and 3.0 micrograms/kg/day, in successive 2-month treatment periods, with monitoring of overnight 12 h episodic GH secretion and toxicity measures at the end of each period. During a fourth 2-month period, they received 3 micrograms/kg GHRP-2 together with 3 micrograms/kg s.c. GHRH. Serum levels of IGF-I and IGFBP-3 were also measured, and stadiometer height measurements were recorded. GHRP-2 administration produced a dosewise increase in overnight GH secretion. GH profiles showed that the effect of GHRP-2 injections was relatively brief, with little effect upon GH secretion later in the night. Serum levels of IGF-I and of IGFBP-3 did not increase. Growth velocity was higher during GHRP-2 treatment than during pretreatment and post-treatment evaluations. There were no side effects or toxicities observed. Thus GHRP-2 is well tolerated and is able to stimulate GH secretion. Formulations or routes of administration that allow for a longer duration of action will likely be needed to use GHRP-2 in therapy.

Growth hormone in postmenopausal women after long-term oral estrogen replacement therapy.

Studies of estrogen effects on growth hormone (GH) and its pulsatile release in postmenopausal women have typically utilized estrogen replacement therapy (ERT) of relatively short duration (days to weeks). The purpose of this study was to compare GH measures from healthy postmenopausal women who were on oral ERT for 3 years or more (n = 24; mean ERT duration = 16.1 years) with women not on ERT (NERT; n = 40). Blood samples were drawn remotely every 20 min for 24 h and then analyzed for mean 24-h GH, mean GH during sleep, and mean 24-h insulin-like growth factor-I (IGF-I). GH peak analyses were also performed. Mean 24-h GH and GH during sleep were significantly higher and IGF-I was significantly lower in ERT women compared with NERT women. In addition, use of long-term ERT was associated with more GH peaks relative to women not on ERT, but no change in GH peak amplitude or area. GH was not related to age in either group. GH was strongly and negatively correlated with measures of adiposity in NERT women but not in ERT women. In conclusion, long-term oral ERT is associated with increased circulating GH and decreased IGF-I levels, even after many years of treatment.

Reproductive dysfunction in women with Albright's hereditary osteodystrophy.

Most individuals with Albright's hereditary osteodystrophy (AHO) have deficient expression or function of G(s alpha), the alpha subunit of the guanine nucleotide binding protein that stimulates adenylyl cyclase, and are resistant to parathyroid hormone (PTH) and other hormones that act via stimulation of adenylyl cyclase. To determine the incidence and etiology of ovarian dysfunction in women with AHO, we examined the reproductive history and hypothalamic-pituitary-ovarian axis in 17 affected women aged 17-43 yr. All patients had typical PTH resistance and an approximately 50% reduction in erythrocyte G(s alpha) activity, (0.43 +/- 0.03 vs. 0.92 +/- 0.08 for normal control subjects, P < 0.001). Fourteen of the 17 patients (76%) were oligomenorrheic or amenorrheic, more than half had delayed or incomplete sexual development, and only two had a history of earlier pregnancy. Most women were mildly hypoestrogenic, with normal to slightly elevated serum gonadotropin levels. Computer analysis of 24 hour LH measurement showed that the frequency of LH peaks/24 h in AHO women varied widely, but as a group they were not statistically different from a group of normal women studied in the early follicular phase. Administration of 100 microg synthetic GnRH produced normal FSH and LH responses. We conclude that reproductive dysfunction is common in women with AHO and probably represents partial resistance to gonadotropins.

Potential applications of GH secretagogs in the evaluation and treatment of the age-related decline in growth hormone secretion.

The two classes of GH secretagogs--GH-releasing hormone (GHRH) and the GH-releasing peptides and their analogs (GHRP's)--retain their ability to endogenous GH secretion in healthy and frail elderly subjects. They have very limited utility in assessment of the state of the GH/IGF-I axis except to confirm an intact pituitary, but they are attractive potential alternatives to GH as therapeutic agents. There is wide interest in the possibility that elevating GH and IGF-I might increase muscle mass, physical strength and performance, and possible sleep and cognition in aging. The GH secretagogs, like GH, can produce a sustained stimulation of this axis; in contrast to GH, they preserve feedback regulation at the pituitary level and stimulate a near-physiologic pulsatile pattern of GH release. GHRP's and their nonpeptide analogs are also active when given orally, a significant practical advantage. Short-term treatment studies have shown that GHRH and the GHRP's can enhance GH secretion and elevate IGF-I and IGFBP-3 levels; that GHRH may promote sleep; and that these agents are generally well tolerated. Longer-term studies assessing effects upon body composition and physical and psychological function are underway.

Successful 6-month endurance training does not alter insulin-like growth factor-I in healthy older men and women.

BACKGROUND: Lean body mass, strength, and endurance decline with advancing age, changes paralleled by declines in anabolic hormones, including growth hormone (GH) and insulin-like growth factor-I (IGF-I). Acute exercise has been shown to stimulate the GH/IGF-I axis, and long-term exercise increases GH. This study examined the effect of endurance training on IGF-I in healthy older men and women. METHODS: Thirty-one healthy older men (66.9 +/- 1.0 yrs, mean +/- SEM) and 21 healthy older women (67.1 +/- 1.7 yrs) were randomized to either 3d/wk, 6-month endurance (ET3) or stretching/flexibility (SF3) protocols. Another group of 15 healthy older men (69.0 +/- 1.3 yrs) participated in a more intensive 5d/wk, 6-month endurance protocol (ET5). Before and after training, subjects were weight stabilized and participated in maximal exercise tolerance testing, body composition assessment, and fasting blood sampling. RESULTS: ET3 training resulted in a significant increase (14%) in maximal aerobic power (VO2max), significant decreases in body weight (BW), fat mass (FM), and waist/hip ratio (WHR), and a significant increase in fat-free mass (FFM). No significant VO2max or body composition changes were observed in the SF3 group. For the ET5 group, a significant increase (22%) in VO2max and significant decrease in BW, FM, and WHR were observed. No significant changes in IGF-I were observed for any of the three groups. Pre- versus post-training IGF-I values were very stable (r = .86, p < .001) across subjects. CONCLUSIONS: Within-subject basal levels of IGF-I in healthy seniors were extremely stable between pre- and post-training assessments. Two endurance training protocols of magnitudes sufficient to significantly increase aerobic capacity and decrease measures of body adiposity did not significantly increase basal levels of IGF-I in healthy older men and women.

A prospective controlled study of luteal and endometrial abnormalities in an infertile population.

OBJECTIVE: To investigate whether luteal and endometrial abnormalities occur more frequently in an infertile population and thus contribute to infertility. DESIGN: Prospective controlled clinical study. SETTING: Outpatient clinic in an academic research institution. PARTICIPANTS: Thirty-three fertile controls and 31 infertile women without ovulatory disorders, tubal disease, or male factors. INTERVENTIONS: All women underwent an endometrial biopsy 9 days after the LH surge followed by an IM injection of 5,000 IU hCG. Blood samples were drawn immediately before hCG administration for serum P and placental protein 14 (PP14) measurements, at 6 hours after hCG stimulation for serum P concentrations, and on day 5 after hCG administration for serum PP14 levels. MAIN OUTCOME MEASURES: Histologic dating of the endometrium and serum P and PP14 measurements. RESULTS: Abnormal endometrial biopsies occurred more frequently in infertile (43%) than in fertile women (9%). Except for one case, these specimens were not associated with low hCG-stimulated P levels. Serum PP14 measurements varied widely and did not discriminate subjects with abnormal endometrial development. CONCLUSIONS: Disruption of endometrial maturation without a concomitant defect of the corpus luteum occurs more frequently in an infertile population and thus may contribute to infertility.

Ovulation induction using s.c. pulsatile gonadotrophin-releasing hormone: effectiveness of different pulse frequencies.

To determine the ovarian response to a fixed dose of gonadotrophin-releasing hormone (GnRH) administered s.c. at four different pulse frequencies, 20 patients with hypothalamic amenorrhoea were treated over 41 cycles using a dose of 20 ng/kg/pulse. These patients were randomly assigned to receive GnRH at pulse frequencies of 60, 90, 120 or 180 min. GnRH was administered s.c. using portable infusion pumps. Subjects were paid volunteers with a diagnosis of hypothalamic amenorrhoea. All patients had low to less than detectable serum concentrations of luteinizing hormone and follicle stimulating hormone on 8 h serial sampling, and normal serum concentrations of prolactin and androgen, including androstenedione, testosterone and dihydroepiandrosterone sulphate. Six of the 20 patients were enrolled in the protocol to achieve a pregnancy, while 14 were volunteers using a barrier method of contraception. Highest ovulation rates were achieved using pulse frequencies of 90 and 120 min (60 and 88% of cycles respectively). Ovulation occurred significantly less often with frequencies of 60 and 180 min (12 and 38% respectively; P

The effects of beta 1-adrenergic blockade on the growth response to growth hormone (GH)-releasing hormone therapy in GH-deficient children.

Acute suppression of SRIH secretion with a beta-adrenergic antagonist can increase the GH response to GHRH. To determine whether chronic beta-blockade could enhance the growth-promoting effects of GHRH therapy, we conducted a double blind, placebo-controlled, randomized, cross-over trial of coadministration of the selective beta 1-antagonist atenolol together with GHRH in 11 GH-deficient children. In randomly chosen order, each patient received two 12-month treatment periods with a single daily injection of GHRH (20 micrograms/kg, sc, at bedtime), plus daily oral administration of either atenolol (1 mg/kg) or placebo. The growth velocity increased, rising from a mean +/- SD of 2.6 +/- 0.4 cm/yr before treatment to 5.4 +/- 1.0 cm/yr during the first year of treatment with GHRH plus placebo and to 6.8 +/- 1.2 cm/yr during the first year of treatment with GHRH plus atenolol. The mean growth velocity during treatment with GHRH plus atenolol was significantly greater than that observed during GHRH plus placebo (P < 0.05). After cross-over, however, during the second year of therapy, we did not observe any significant differences in growth velocity between the two groups (4.2 +/- 1.4 vs. 3.9 +/- 0.8 cm/yr during treatment with GHRH plus placebo and GHRH plus atenolol, respectively). The mean 24-h serum GH levels were 1.4 +/- 0.9 micrograms/L during the baseline period, 1.3 +/- 0.2 and 2.0 +/- 1.4 micrograms/L during the first year of GHRH plus placebo and GHRH plus atenolol, respectively (P = NS), and 2.7 +/- 1.4 and 1.4 +/- 0.4 micrograms/L during the second year of GHRH plus placebo and GHRH plus atenolol, respectively (P < 0.05). This is the first demonstration that alteration of neurotransmitter action can enhance the therapeutic response to a hypothalamic releasing factor.

Higher plasma IGF-1 levels are associated with increased delta sleep in healthy older men.

BACKGROUND: Sleep quality declines with age, with less time in deep or slow wave sleep (SWS) and reduced amplitude of the delta waves that characterize it. Age-related declines also occur in lean body mass, growth hormone (GH), and insulin-like growth factor 1 (IGF-1). These changes in sleep quality and anabolic status may be related, as administration of GH or growth hormone releasing hormone (GHRH) can enhance SWS and decrease awakenings in young men. Here we examine the relationship between plasma IGF levels and delta sleep quality in older men. METHODS: The sleep EEG of 30 healthy elderly men (64 +/- 6 yrs; range 50-75) was recorded on the second of 2 consecutive nights. Plasma samples were drawn within 3 weeks of EEG recording, and IGF levels were assayed by RIA after acid extraction. RESULTS: IGF explained 28% (semi-partial correlation coefficient r = .53; p = .003) of the variance in average delta energy per epoch of SWS, after age-related variance was removed. Higher IGF was associated with higher average delta energy. Similar results were obtained for total delta energy during SWS (r = .37, p = .04) 4nd time spent in SWS (r = .42, p = .02). Other measures of sleep quality (e.g., wakefulness, REM sleep) were not correlated with IGF. The IGF delta relationship was minimally influenced by moderator variables such as thyroxine (T3, T4), and/or body mass index (BMI). CONCLUSION: We conclude that age-adjusted IGF levels in healthy senior men co-vary significantly with SWS and the delta energy that characterizes it.

Pulsatile GnRH stimulates normal cyclic ovarian function in amenorrheic lactating postpartum women.

The postpartum period is characterized hormonally by elevated levels of PRL and low levels of gonadotropins and sex steroids. In breast feeding, this state of postpartum amenorrhea can persist for an extended period, even though PRL levels decrease slowly. Although the action of PRL on multiple target sites has frequently been suggested as the cause of this ovarian quiescence, a suckling-induced alteration in hypothalamic gonadotropin-releasing hormone (GnRH) production has also been hypothesized. To test this latter hypothesis, we provided a uniform pulsatile GnRH stimulus to eight exclusively breast-feeding women for an 8-week duration beginning at 4 weeks postpartum. Five women with functional hypothalamic amenorrhea served as a comparison group. All women received GnRH administered at a dose of 200 ng/kg every 90 min sc via a portable infusion pump. Serial blood sampling for LH, FSH, and PRL was performed weekly for 5 h at 10-min intervals beginning immediately before initiation of GnRH, during the period of GnRH, and 1 week after the cessation of GnRH. The women collected daily urine aliquots for estrone-3-glucuronide, pregnanediol-3-glucuronide, and LH determinations. Serial transvaginal sonography was used to monitor follicular development. Before GnRH treatment the urinary steroid and serum gonadotropin levels of the two groups were low and similar. As expected, PRL levels were higher in the postpartum women (87 micrograms/mL vs. 4.25 micrograms/L, P < 0.05). After initiation of pulsatile GnRH, LH values increased and FSH values decreased in both groups. The LH increase with GnRH was significantly greater in the breast-feeding group than in the hypothalamic amenorrhea group (19.75 mIU/mL vs. 12.34 mIU/mL, P < 0.05). Analysis of pulse frequency and amplitude revealed a nearly complete 1:1 induction of LH pulses by the exogenous GnRH in both groups, with the breast-feeding group showing a greater amplitude (12.26 mIU/mL vs. 5.34 mIU/mL, P < 0.05). The cycle lengths, urinary steroids, and vaginal ultrasonography demonstrated a more rapid initial ovarian responsiveness in the breast-feeding group, as determined by the length of the first follicular phase. The breast-feeding group also showed a brisker ovarian response, as evidenced by a greater number of follicles that were 12 mm or greater (2.3 vs. 1.2, P < 0.05), and a greater luteal phase peak and integrated pregnanediol excretion, respectively (3.02 micrograms/L creatinine and 39.87 micrograms/L creatinine/cycle vs. 1.89 micrograms/L creatinine and 7.69 micrograms/L creatinine/cycle, P < 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Growth hormone (GH) responses to GH-releasing peptide and to GH-releasing hormone in GH-deficient children.

The GH-releasing peptides (GHRPs) are a family of hexa- and heptapeptides that specifically stimulate GH secretion in normal adults and children. They would be an attractive potential form of therapy for GH deficiency (GHD) if they are also active in these patients. Their action, however, appears to result at least in part through hypothalamic responses, which may be impaired in GHD, and their ability to evoke a GH response in these patients must therefore be directly examined. We studied GH responses to the heptapeptide GHRP-1 in 22 prepubertal children with previously documented GHD and growth failure and compared them to responses to GHRH and the two peptides administered together. Patients received 1 microgram/kg GHRH-(1-44)NH2, 1 microgram/kg GHRP-1, or both, in random order. Tests were separated by at least 1 week. GHRP-1 evoked a significant GH response in 60% of the patients, comparable to the 68% who responded to GHRH. The magnitudes of the peak responses were similar (7.5 +/- 8.0 micrograms/L to GHRP-1 and 11.2 +/- 12.1 to GHRH), although the duration of the GH rise was briefer after GHRP-1. Both responses were lower than those previously observed in normal subjects. There was a marked synergy in responses when the two were given together; the GH peak (34.2 +/- 44.8 micrograms/L) significantly exceeded the sum of the individual responses, and the proportion of patients who responded (86%) was also higher. Thus, despite the absence of endogenous GHRH reflexes in most patients with GHD, these children can respond to GHRP-1 similarly to GHRH, and GHRP-1 can markedly enhance the response to GHRH. These results suggest that GHRPs or their analogs could form the basis for therapy of GHD.

Growth hormone (GH) modulates insulin-like growth factor I (IGF-I) and type I IGF receptor mRNA levels in the ovary of prepubertal GH-deficient rats.

In order to explore the potential role of growth hormone (GH) in modulating insulin-like growth factor I (IGF-I) gene expression in the prepubertal rat ovary, female rats were rendered GH deficient by neonatal administration of monosodium glutamate (MSG). One group of rats received vehicle and served as the control. At 21 days of age, MSG-treated rats received either GH or vehicle for 2 weeks. On days 21, 24, 28 and 31 animals were weighed and subsets were sacrificed for liver RNA extraction. The remaining animals were sacrificed at day 35 when livers and ovaries were collected, and serum was obtained for GH determinations. The IGF-I mRNA levels were estimated by Northern blots and corroborated further by slot-blot analysis. The MSG-treated rats had lower body weights (p < 0.01) and GH levels (p < 0.05) than controls. Growth hormone replacement significantly accelerated the weight gain of MSG-treated rats. At day 24 and thereafter, three RNA IGF-I species (7.5, 1.8 and 0.8-1.2 kB) were seen in the liver. In the ovary, at age 35 days, two major IGF-I mRNA species (7.5 and 0.8-1.2 kb) were seen. The MSG treatment consistently reduced the levels of both IGF-I mRNA species in the ovary. Growth hormone administration partially restored their expression, both in the liver and in the ovary. In addition, ovarian type IIGF receptor mRNA levels were increased in the MSG-treated rats when compared to controls. This trend was reversed by GH replacement.(ABSTRACT TRUNCATED AT 250 WORDS)