Plasma aldosterone concentration at delivery and during the newborn period.

Aldosterone concentrations in plasma of women on normal sodium intake undergoing cesarean section were 3.7+/-1.4 ng/100 ml (mean+/-1 SD). These values were significantly lower (P < 0.001) than those observed in mothers on normal sodium diet, delivered by the vaginal route (14.9+/-7.0 ng/100 ml). A significant elevation (P < 0.001) of the concentrations was found if the mothers had been on sodium restriction and/or diuretics (44.9+/-24.2 ng/100 ml). In supine position, adult nonpregnant subjects have aldosterone concentrations in plasma of 1.7+/-1.4 ng/100 ml on normal sodium intake and of 16.7+/-8.1 ng/100 ml on low sodium diet.Simultaneous determinations of aldosterone levels in cord blood showed that cord values were significantly higher than those of the corresponding mother (P < 0.01 by paired t test). However, values in cord blood of infants born to mothers on a normal sodium intake were significantly lower (P < 0.005) than those of infants whose mothers had required low sodium diet and/or diuretics during their pregnancy. Aldosterone concentrations in plasma of infants 1-72 hr of age and born to mothers on normal sodium intake were 25.9+/-11.7 ng/100 ml (mean +/-1 SD). These values were significantly lower (P < 0.005) than those of infants born to mothers on restricted sodium intake with or without diuretics (80.3+/-54.4 ng/100 ml). The concentrations at birth were not significantly different from those observed during the first 3 days of life (P > 0.6).

The regulation of aldosterone secretion in anephric man.

The regulation of aldosterone secretion in anephric man was investigated in studies on nephrectomized patients who were being intermittently hemodialyzed while awaiting renal transplantation. The effects of supine and upright posture on the concentration of plasma aldosterone on the 1st day postdialysis and on a 3rd or 4th day postdialysis were compared to the effects of postural variation in normal subjects who were on a low sodium intake and on a high sodium intake. In contrast with the normal subjects who exhibited higher concentrations of plasma aldosterone after 2 hr of upright posture than in the supine position and low concentrations of plasma aldosterone on a high sodium intake, the anephric patients showed less consistent variations in plasma aldosterone due to changes in posture and exhibited higher concentrations of plasma aldosterone on the 3rd or 4th day postdialysis, despite an increase in body weight, than on the 1st day postdialysis. The increase in the concentration of plasma aldosterone in the anephric patients between the 1st day postdialysis and the 3rd or 4th day postdialysis indicates that aldosterone secretion is not responding primarily, in this situation, to volume-related stimuli. There was a high degree of correlation between the concentration of plasma aldosterone and the corresponding levels of serum potassium concentration, which also rose significantly between the 1st day postdialysis and the 3rd or 4th day postdialysis. Furthermore, when potassium accumulation between dialyses was prevented in three of these patients, the concentration of plasma aldosterone fell to minimally detectable levels. The results of these studies suggest that the primary regulator of aldosterone secretion in the absence of the kidneys is potassium.

An improved in vitro bioassay for follicle-stimulating hormone (FSH): suitable for measurement of FSH in unextracted human serum.

FSH bioactivity was measured by means of FSH-dependent aromatase activity (conversion of androgen substrate to estradiol). Assay sensitivity was optimized by the use of immature (7-10 days old) rats as Sertoli cell donors, serum-free medium for incubation, phosphodiesterase inhibitor (methylisobutylxanthinine), serial dilution of FSH in medium containing 1% BSA, delayed addition of FSH for 72 h after cell plating, and 19-hydroxyandrostenedione (2.5 X 10(-6) M) as the aromatizable androgen substrate. The method consisted of subjecting the decapsulated immature rat testes to a 2-step collagenase dispersion, plating the cells in medium [Dulbecco's Modified Eagle's Medium-Ham's F-10 (1:1)] containing growth factors and methylisobutylxanthinine for 72 h, adding increasing doses of FSH to the standard curve or small volumes of serum to the test vials as well as 19-hydroxyandrostenedione for 24 h, and measuring estradiol by RIA in dilutions of the medium. Using NIAMDD human (h) FSH-2 as the bioassay standard, the useful range of the assay was 0.01-5.0 ng/ml. Specificity was determined by the addition of graded doses of hLH, hTSH, ACTH, hGH, hPRL, and hCG. The minor degree of FSH bioactivity observed in a few hormone preparations was accounted for by the degree of FSH contamination in them. Mean intra- and interassay coefficients of variation were 9% and 11%, and the index of precision was 0.049. This bioassay was used to determine the bioactive FSH content of pituitary extracts, tissue culture media, elutions from columns, and isoelectrically focused samples. More importantly, small quantities of human sera gave responses parallel to the standard curve in a minimum of two dilutions. The bio- to immunoreactive ratios, expressed as the mean +/- SEM (NIAMDD-hFSH-2), were 0.66 +/- 0.2 in boys (n = 6), 0.78 +/- 0.2 in pubertal girls (n = 6), 1.18 +/- 0.2 in men (n = 13), 1.24 +/- 0.1 in postmenopausal women (n = 30), 1.94 +/- 0.3 in the follicular phase (n = 19), 6.2 +/- 1.4 in the ovulatory phase (n = 19), and 1.6 +/- 0.4 in the luteal phase (n = 19) of the normal menstrual cycle. These results indicate that the bio- to immunoreactive hFSH ratio in the circulation, is dependent upon the hormonal milieu of the subject.

Characterization and application of a radioimmunoassay for reduced, carboxymethylated human luteinizing hormone alpha-subunit.

We have established a double antibody RIA using a rabbit antiserum prepared against reduced, carboxymethylated (RCXM) human LH alpha-subunit, with RCXM-alpha as tracer and standard. This antiserum did not cross-react with any native gonadotropins or subunit, and reacted only weakly with RCXM-alpha. A tryptic digest of RCXM alpha-subunit was completely reactive, while chymotryptic digestion abolished all immunoreactivity. By testing with separate tryptic fragments, the recognition site could be localized to a segment close to the amino-terminus of the peptide chain. When applied to measurement of serum and urine, an immunoreactive species, parallel to RCXM alpha-subunit by serial dilution, was found in concentrations of 1-2 ng/ml in serum and 3-4 ng/ml in urine. Similar levels of the immunoreactive component were found in conditions of elevated gonadotropins (e.g. pregnancy) as well as gonadotropin deficiency(panhypopituitarism and Kallmann's syndrome). After stimulation with LHRH, no rise was noted at times up to 6 h despite the fact that both LH and LH-alpha were elevated. The data indicate that the sequence-specific antiserum may be detecting an immunoreactive form of alpha-subunit of LH whose kinetics of appearance and disappearance differs from those of the native subunit.

Conversion of radiolabeled human growth hormone into higher molecular weight moieties in human plasma in vivo and in vitro.

Purified human growth hormone (hGH) was iodinated with 131I ([131I]iodo-hGH) and purified on Sephadex G-100. The monomeric [131I]iodo-hGH (mol wt about 20,000 daltons) was injected as a bolus iv in healthy volunteers and plasma obtained at 10, 20, and 40 min. Then continuous infusion with [131I]-iodo-hGH was started and further plasma samples obtained after 120 min when a plateau of immunoreactive hGH (IR-hGH) had been attained. In one individual the bolus injection was followed further to 60 and 120 min. Fresh plasma was immediately chromatographed on Sephadex G-100 and the IR-hGH profiles evaluated. In all instances following iv injection, larger and occasionally smaller immunoreactive moieties than the injected [131I]iodo-hGH appeared. When [131I]iodo-hGH was incubated at 37 C with fresh human plasma from 4 different individuals from 10 to 120 min, the larger molecular weight forms, noted in the in vivo studies, were again demonstrable. Only the monomeric [131I]iodo-hGH was found when [131I]iodo-hGH was incubated at 37 C for 120 min with human serum albumin or gamma globulin.

Luteinizing hormone-releasing hormone does not inhibit testosterone production in rat interstitial cells in vitro.

The effects of LHRH and a potent LHRH agonist (LHRHa) on invitro testosterone production by enzyme-dispersed rat interstitial cells were evaluated. In a series of in vitro experiments, neither basal nor human menopausal gonadotropin (hMG)-stimulated testosterone production were significantly affected by doses of LHRH or LHRHa ranging from 10(-12)--10(-5) M. In addition, adult male rats were treated chronically with once daily injections of LHRH or LHRHa (2 micrograms/rat) or the vehicle for 1--7 days and decapitated 24 h after the last injection, and their testes were removed and weighed. Testicular weights decreased significantly by day 3 and were maximally decreased by day 6. In vitro testosterone production in response to 1--5 mIU human menopausal gonadotropin was markedly impaired (greater than 50%) in cells from rats treated with LHRHa for 2 days or longer and in rats treated with LHRH longer than 3 days. These data indicate that 1) LHRH and LHRHa do not alter in vitro testosterone production by dispersed rat interstitial cells and 2) interstitial cells of rats pretreated with LHRH and LHRHa exhibited impaired in vitro testosterone production. The data do not, however, rule out a direct effect of LHRH or LHRHa on testicular systems other than those involved in steroidogenesis.

Insensitivity of bonnet monkeys to (D-Ala6, Des-Gly10) LHRH ethylamide, a potent new luteinizing hormone releasing hormone analogue in rats and mice.

The Luteinizing Hormone Releasing Hormone (LHRH) activity of (D-Ala6, Des-Gly10) LHRH ethylamide was compared with that of LHRH in oöphorectomized bonnet monkeys by determining serum LH and FSH concentrations at various time intervals after a sc injection of 100 mug of LHRH and either 100 mug or 1 mg of the analogue. Following administration of synthetic LHRH, a significant rise in both serum LH and FSH was observed. In contrast, no discernible change in serum gonadotropin concentrations was noted following injection of the analogue (D-Ala6, Des-Gly10) LHRH ethylamide, previously reported to have greatly increased potency in rats and mice.

Pulsatile administration of gonadotropin-releasing hormone does not alter the follicle-stimulating hormone (FSH) isoform distribution pattern of pituitary or circulating FSH in nutritionally growth-restricted ovariectomized lambs.

The experimental induction of puberty by GnRH administration to prepubertal lambs increases serum bioactive FSH (B-FSH) as measured in the rat Sertoli cell aromatase induction bioassay. Serum immunoreactive FSH (I-FSH) levels are unchanged. The increase in serum B-FSH is associated with an increase in the proportion of less acidic and more biopotent FSH serum isoforms. However, it is unknown if this effect of GnRH on serum FSH microheterogeneity is direct or mediated by gonadal factors. We have used the nutritionally growth-restricted ovariectomized lamb as a model of the neuroendocrine regulation of FSH isoform microheterogeneity. With this model, the hypothalamic-pituitary component of the neuroendocrine axis may be isolated from gonadal factors. In the present study, using the nutritionally growth-restricted ovariectomized lamb as a model, we investigated the role of GnRH on the regulation of FSH microheterogeneity. Specifically, we tested the hypothesis that GnRH increases the proportion of the less acidic (more biopotent) serum FSH isoforms. As an in vitro correlate, we investigated the effect of GnRH on gonadotropin secretion and FSH isoform distribution in ovine pituitary explant cultures. Seven ovariectomized nutritionally restricted lambs were administered GnRH (i.v., 2 ng/kg) for 36 h (at 2-h intervals for 24 h, then hourly for the final 12 h). Six others served as controls. Blood samples were withdrawn at 12-min intervals during the last 4 h for the measurement of serum immunoactive LH (I-LH) and I-FSH. Pituitary homogenates and serum from four animals from each group were individually chromatofocused, and the FSH isoform distribution patterns were determined. Pulsatile administration of GnRH to nutritionally growth-restricted lambs increased circulating I-LH concentrations from 0.6 +/- 1.0 to 5.9 +/- 3.1 ng/ml (P < 0.01), but did not significantly change circulating I-FSH (4.9 +/- 1.8 vs. 11.5 +/- 4.2 ng/ml) nor B-FSH concentrations (3.9 +/- 1.2 vs. 5.7 +/- 1.5 ng/ml). The pituitary content of I-FSH, B-FSH, and I-LH were unchanged. Neither serum nor pituitary FSH isoform distribution patterns were altered by pulsatile GnRH administration. However, compared to the pituitary FSH isoforms, a higher percentage of circulating FSH isoforms eluted in the salt peak of both groups of lambs. Similar to the in vivo studies, in vitro, GnRH increased the release of I-LH, as well as I-FSH, from pituitary explants, but did not significantly change the FSH isoform distribution in either the pituitary explant or media.(ABSTRACT TRUNCATED AT 400 WORDS)

Bioactivity of human growth hormone in serum: validation of an in vitro bioassay.

GH, in clinical practice, is determined by RIA, but RIA estimates may not accurately reflect serum GH bioactivity. The available measures of GH bioactivity lack either sensitivity, specificity, or a physiologically relevant end point. The objective of this research was to develop a physiologically relevant GH bioassay which would not only measure the bioactivity of purified GH preparations, but would also have sufficient sensitivity to measure GH bioactivity in human serum. The method consisted of incubating murine 3T3-F442A adipocytes in serum-free medium containing BSA, 14C-glucose, and increasing concentrations of GH or test materials for 24 h, followed by measurement of conversion of glucose to lipid. Interference by nonspecific serum factors was reduced by the addition of 10 micrograms/liter insulin, 25 nM dexamethasone, and 37 nM estradiol to the medium. In the presence of 10 micrograms/liter insulin, 50 micrograms/liter insulin-like growth factor-1 did not alter the ability of GH to suppress lipid accumulation. Epinephrine and glucagon could suppress lipid accumulation but only at concentrations greatly in excess of the physiological range in serum. Twenty two thousand dalton hGH produced dose-dependent suppression of lipid accumulation which was linear between 0.625 and 10 micrograms/liter (r = 0.926; P = 0.0001) with a half-maximal response of 3.0 +/- 0.2 micrograms/liter (n = six experiments). The intra- and interassay coefficients of variation were 7% and 19%, respectively. The assay was specific for GH since addition of human PRL produced suppression of lipid accumulation only at concentrations where contamination of the preparation by GH became a significant factor. ACTH also suppressed lipid accumulation but only at doses of 1000 micrograms/liter or greater. Human placental lactogen and hLH, hFSH, and hTSH did not cross-react with GH in this assay. Addition of human serum did not alter the slope of ED50 of the GH dose-response curve. Pools of serum from prepubertal and pubertal boys and girls, subjects treated with arginine or insulin, a diabetic girl, and a boy with gigantism who had a serum GH content of 80 micrograms/liter by RIA and 40 micrograms/liter by bioassay, produced dose response curves parallel to that of the GH standard curve. Serum from patients with hypopituitarism did not produce significant suppression of lipid accumulation in any assay. Recovery of 5 micrograms/liter GH added to human serum was 94%. Twenty thousand dalton GH also suppressed lipid accumulation in this assay, but was 2-fold less potent than 22,000 dalton GH.(ABSTRACT TRUNCATED AT 400 WORDS)

Bioactive follicle-stimulating hormone release in nutritionally growth-retarded ovariectomized lambs: regulation by nutritional repletion.

The nutritionally growth-retarded ovariectomized lamb provides a model system to investigate the regulation of immunoreactive and bioactive FSH release in the absence of feedback effects of ovarian products. We examined the acute effects of nutritional repletion on FSH release in this model. Five March-born lambs were weaned at 7 weeks of age and placed on a limited diet. All were ovariectomized at 31 weeks. At 37 weeks, they were fed ad libitum for 14 days. Blood samples were collected at 12 min intervals for 4 h on day -1 (restricted) and days 2, 7, and 14 of ad libitum feeding, and serum FSH concentrations were measured by both RIA and a Sertoli cell aromatase in vitro bioassay. Mean concentrations of serum immunoreactive FSH (I-FSH) and the bioactive FSH (B-FSH) increased 2- and 3-fold, respectively, after ad libitum feeding for 14 days. Pulse analyses by two objective computerized programs, DETECT and CLUSTER, revealed the presence of FSH pulses (predominantly B-FSH) during the restricted phase, as well as ad libitum fed phases, at times where I-LH pulses were not detected. In contrast to the increases in I-LH pulse frequency during ad libitum fed states, FSH pulse frequency remained stable whereas pulse amplitude increased. In addition, the overall B-FSH pulse amplitudes were 57 +/- 7% (mean +/- SE of three different pulse analyses) greater than I-FSH pulse amplitudes, implying preferential enrichment of FSH bioactivity. The results suggest that the mechanisms governing both the quantitative and qualitative changes in circulating FSH concentrations are extremely sensitive to changes in level of nutrition. The asynchronous occurrence of FSH pulses in the absence of I-LH pulses suggests that FSH may be more sensitive to small changes in GnRH secretion than I-LH, or that a hypothalamic releasing factor specific for FSH may be released.

Metabolic interfaces between growth and reproduction. II. Characterization of changes in messenger ribonucleic acid concentrations of gonadotropin subunits, growth hormone, and prolactin in nutritionally growth-limited lambs and the differential effects of increased nutrition.

Previous studies show that limited nutrition in the ovariectomized lamb results in an impairment of LH and FSH secretion, a phenomenon that is rapidly reversible by increasing the level of nutrition and independent of ovarian steroid feedback. The present study characterizes the biosynthesis of pituitary hormones in the nutritionally growth-limited female lamb by measuring steady state mRNA concentrations. These changes were examined relatively to pituitary and serum hormone concentrations to establish the relationship(s) of synthesis and secretion in response to nutritional manipulation. Ad libitum feeding of nutritionally growth-restricted ovariectomized lambs for 14 days resulted in an increase in the frequency of episodic LH release, thereby increasing mean serum LH concentrations (P less than 0.001). Similarly, mean circulating concentrations of FSH were increased (P less than 0.001). By contrast, serum GH concentrations were lowered significantly as a result of ad libitum feeding (P less than 0.05). Serum PRL concentrations remained unchanged. Although pituitary LH and PRL concentrations were also unchanged in response to increased nutrition feeding, FSH and GH concentrations increased (P less than 0.05). Short-term ad libitum feeding of the chronically food-restricted lamb resulted in significant changes in mRNA concentrations for all hormones except PRL. The concentrations of gonadotropin subunit mRNAs (i.e. alpha, LH beta, and FSH beta) were all significantly higher in response to increased nutrition (P less than 0.001). GH mRNA was also affected; however, feeding decreased concentrations (P less than 0.001). The results demonstrate that an increase in the level of nutrition in the restricted diet lamb produces profound changes in the synthesis, storage, and secretion of LH, FSH, and GH. These changes appear to be coordinated, although the response differs depending upon the hormone.

Circulating bioactive follicle-stimulating hormone and less acidic follicle-stimulating hormone isoforms increase during experimental induction of puberty in the female lamb.

The pubertal process with its multifaceted neuroendocrine control provides an excellent model for the study of the regulation of FSH heterogeneity. We tested the hypothesis that during the pubertal transition in the female lamb 1) an increase in both pituitary and circulating bioactive FSH concentrations occur and 2) that the increase in bioactivity is associated with a change in the distribution pattern of both pituitary and circulating FSH isoforms. Pituitary and serum immunoreactive (I), and bioactive (B, Sertoli cell bioassay) FSH concentrations were measured in six prepubertal lambs (18 +/- 1 weeks, 29.9 +/- 2.8 kg body weight; mean +/- SE) and compared to those of six others (24.2 +/- 2.2 weeks of age, 41.4 +/- 2.5 kg body weight) during the pubertal transition period. Puberty was synchronized by pulsatile iv administration of GnRH (2 ng/kg every 2 h for 24 h and then at hourly intervals for the next 12 h) in a manner mimicking the I-LH pulse patterns observed during the natural transition to adulthood. Blood samples were collected at 12-min intervals for 4 h from both groups of lambs; for the pubertal group this included the final 32-36 h of GnRH administration. At the end of the study, a 25 ml volume of peripheral blood was collected from both prepubertal and pubertal females for the determination of serum FSH distribution patterns; the lambs were then euthanised, and pituitaries were removed for determination of pituitary hormone content and FSH isoform distribution patterns. In addition, the distribution pattern of I-FSH isoforms in the pituitary and serum from both groups of lambs were compared. The pubertal stages of all lambs were verified by measuring the size of follicles, the circulating concentrations of estradiol (E2) and inhibin, and the I-LH pulse patterns. Prepubertal lambs had low frequency I-LH pulses, small (2-3 mm) size ovarian follicles and low circulating concentrations of E2 (4.1 +/- 0.4 pg/ml) and inhibin (38.0 +/- 2.9 U/ml WHO). By contrast, all the pubertal lambs had hourly I-LH pulse frequency (induced with exogenous GnRH), a large (5-6 mm) follicle (in one lamb a 4-mm follicle), follicular phase levels of E2 (7.1 +/- 0.8 pg/ml), and higher concentrations of inhibin (53.2 +/- 3.1 U/ml).(ABSTRACT TRUNCATED AT 400 WORDS)

Immunoreactive luteinizing hormone, follicle stimulating hormone and their subunits in tissue culture media from normal and adenomatous, human pituitary fragments.

Fragments from 4 human pituitaries removed at surgery from one gonadectomized man and three women (one with Nelson's syndrome, one with Forbes Albright syndrome and one with chromophobe adenoma) were grown in tissue culture. The tissue culture medium was changed at weekly intervals, pooled and applied to a Sephadex G-100 column for gel filtration. In each eluate luteinizing hormone (LH), follicle stimulating hormone (FSH), alpha subunit and the beta subunits of LH and FSH were measured by specific radioimmunoassays. For comparison the pituitary standard LER 907 was similarly studied. LH and FSH were measurable in all studies. LH eluted over a broad area whereas FSH eluted as a much sharper peak. In all culture media and in LER 907 large quantities of alpha subunit were detected. The beta subunits of LH and FSH were not present in the LER 907 standard. LHbeta subunit was present in the culture medium of the pituitary fragments from the castrated man and from the women with Nelson's syndrome and Forbes Albright syndrome but not in that of the woman with chromophobe adenoma. FSHbeta subunit was detectable only in the latter case.

Plasma insulin-like growth factor-I/somatomedin-C in acromegaly: correlation with the degree of growth hormone hypersecretion.

We measured plasma insulin-like growth factor I/somatomedin-C (IGF-I/SmC) concentrations and mean 24-h GH secretion serially before and during therapy with the long-acting somatostatin analog SMS 201-995 in 21 patients with acromegaly. When mean plasma GH was elevated above 12.0 +/- 0.6 (+/- SE) micrograms/L, plasma IGF-I/SmC concentrations were uniformly high, but a decline of mean plasma GH below this value was accompanied by a linear decrease in IGF-I/SmC concentrations (r = 0.89; P less than 0.001). Even mildly abnormal mean GH concentrations (greater than 4.6 but less than 10 micrograms/L) were accompanied by high plasma IGF-I/SmC values. The log dose-response interrelation between mean 24-h plasma GH and IGF-I/SmC concentrations was linear (r = 0.86; P less than 0.001). We conclude that 1) an excellent log dose-response correlation between mean 24-h plasma GH and IGF-I/SmC concentrations is present in patients with acromegaly; 2) normalization of plasma IGF-I/SmC occurs only in patients with mean daily GH output within the normal range; and 3) determination of plasma IGF-I/SmC is an accurate indicator of normalcy of GH secretion and should be used in the diagnosis of active acromegaly as well as in monitoring the progress of therapy.

Gonadotropin determinations in times 3-hour urine collections during the menstrual cycle and LHRH testing.

The usefulness of timed 3-hour urine collections as a substitute for serum gonadotropin (LH and FSH) determinations during the menstrual cycle and during LHRH testing was examined. The timing of the 3-hour urine collection is not important in mature individuals, since no significant temporal trend was found when aliquots were collected every 3 hours throughout two 24-hour periods in one mature woman. Good correlation was found between serum LH and FSH concentrations and the quantity of LH and FSH in timed 3-hour urine specimens throughout normal, ovulatory menstrual cycles in two women. Studies before and during 51 LHRH stimulation tests in normal men, children, and women during different phases of the menstrual cycle and in patients with a variety of hypothalamic-pituitary-gonadal axis disorders were performed. There was good correlation between the quantity of the gonadotropins in time 3-hour urine collections and the mean serum LH and FSH concentrations before and during the LHRH test. The "response area" for serum LH and FSH also correlated well with the amounts of LH and FSH in the urine collected during this period. Therefore, the timed 3-hour urine collection for gonadotropin estimation provides a simple, accurate method for the integration of fluctuating serum concentrations of LH and FSH during such instances of physiologic variability as the menstrual cycle and LHRH stimulation tests.

Exercise induces two types of human luteal dysfunction: confirmation by urinary free progesterone.

We have previously reported that during 2 months of strenuous exercise, untrained young women with documented ovulatory menstrual cycles developed secondary oligoamenorrhea and luteal phase defects. In this study we tested the hypothesis that such abnormalities arise by altered neuroendocrine regulation of menstrual hormone secretion and that weight loss potentiates such effects. We supply a detailed analysis of the 20 cycles, of the total of 53, in which luteal phase abnormalities occurred. During the control month and 2 exercise months, all subjects collected daily overnight urine samples for the determination of LH, FSH, estriol (E3), and free progesterone (P) excretion by RIAs and creatinine by chemical assay. The characteristics of the abnormal luteal phase cycles were determined by comparing the excreted hormone levels and patterns during the control cycles with those of exercise cycles. The area under the curve (AUC) for each hormone was calculated for the follicular and luteal phases of each cycle. Six of the exercise cycles exhibited an inadequate luteal phase. This was characterized by a mean integrated P area of 202.4 (SEM, -61.8) nmol/day.nmol creatinine, compared with 331.7 (SEM, 64.7) during the corresponding control cycles, over a period of 9 or more days after the urinary LH peak to the onset of menses. Fourteen of the exercise cycles exhibited a short luteal phase. This was characterized by a mean integrated P area of 75.9 (30.9) nmol/day.nmol creatinine, compared to 267 (61.7) during the corresponding control cycles, over a span of 8 days or less from the urinary LH peak to the onset of menses. Additional abnormalities occurred only in the short luteal phase cycles. These included an increase in the length and AUC for E3 of the follicular phase and a decrease in the AUC of LH during the luteal phase. We conclude that the initiation of strenuous endurance training in previously ovulating untrained women frequently leads to corpus luteum dysfunction associated with insufficient P secretion and, in the case of short luteal phase cycles, decreased luteal phase length. That exercise may alter the neuroendocrine system is suggested by a delay in the ovulatory LH peak in spite of increased E3 excretion; moreover, less LH is excreted during the luteal phase. The lack of positive feedback to estrogens and decreased LH secretion during the luteal phase could compromise corpus luteum function. In contrast, decreased free P excretion was the sole abnormality noted in menstrual cycles with an inadequate luteal phase.

Analysis of biological and immunological activities in the two pools of LH released during constant infusion of luteinizing hormone-releasing hormone (LHRH) in men.

In response to constant infusion of a submaximal dose of LHRH (0.2 microgram/min for 4 hours), luteinizing hormone (LH) was released in a biphasic pattern in 6 normal men. When the in vitro biologic activity of plasma LH was compared to the immunologic activity throughout the response to LHRH, the B/I ratio remained unchanged (3.6 +/- 0.5, mean +/- SE). Thus, in men the biologic activity of stored LH (acutely releasable) is not different from the presumably newly synthesized hormone that is released as the second pool during prolonged LHRH infusion.

Reproductive function during fasting in men.

To investigate reproductive function during fasting, six men 20-74% over ideal body weight completed an 18-day study consisting of a 3-day control period, a 10-day total fast, and a 5-day refeeding period. All men lost at least 4.1% of total weight and demonstrated ketonemia and ketonuria. The FSH response to LRH (0.2 microgram/min for 4 h) stimulation was significantly lower (P less than 0.05) during fasting and remained so during refeeding. Serum FSH concentrations were significantly lower (P less than 0.05) during the fast in five of six patients compared to those during the control period, whereas serum LH concentrations were unchanged. The effects of fasting on endogenous LH and FSH pulsations were studied by obtaining serum at 20-min intervals for 6 h on days 2, 11, and 16. Neither the amplitude nor the frequency of LH and FSH pulsations changed significantly during fasting or refeeding. Serum testosterone concentrations were significantly lower (P less than 0.025) by fasting day 9 compared to control values. The 24-h urinary excretion of both LH and FSH increased significantly (P less than 0.05) by fasting day 6 and reached a maximum by fasting day 8. Urinary LH excretion did not return to normal after 3 days of refeeding, whereas urinary FSH excretion returned to baseline by the first day of refeeding. We conclude that during short term fasting in obese men: 1) serum FSH concentrations decrease, 2) the pituitary responsiveness of FSH and LRH is blunted, 3) serum testosterone decreases, and 4) the urinary excretion of both LH and FSH increase.

alpha-Subunit and gonadotropin responses to luteinizing hormone-releasing hormone in hyperprolactinemic women before and after bromocriptine.

alpha-Subunit and gonadotropin responses to a LHRH infusion (0.2 micrograms/min) for 4 h were studied in eight hyperprolactinemic amenorrheic women, ages 23-40, and in five normal women in the early follicular phase of the menstrual cycle. Basal alpha-subunit and LH concentrations were comparable to normal women; however, basal FSH concentrations were significantly (P less than 0.05) lower. Peak serum alpha, LH, and FSH concentrations during the LHRH infusion were significantly higher than controls (P less than 0.01, P less than 0.05, and P less than 0.01, respectively). Gel chromatography of serum confirmed the presence of both free alpha-subunit and intact LH which had normal biological activity. Six of the women were restudied in the early follicular phase of the cycle after return of normal ovulatory function and normalization of serum PRL concentrations. During bromocriptine therapy, peak serum alpha, LH, and FSH concentrations decreased significantly (P less than 0.02, P less than 0.05, and P less than 0.001, respectively) and were comparable to control subjects. The changes in serum alpha and gonadotropin responses to the LHRH infusion during bromocriptine therapy occurred independently of the serum estradiol concentrations. Abnormalities in the regulation of alpha-subunit and gonadotropin secretion are present in hyperprolactinemia. These abnormalities reverse with bromocriptine therapy and may occur independently of changes in gonadal steroids.

Changes in serum immunoreactive and bioactive growth hormone concentrations in boys with advancing puberty and in response to a 20-hour estradiol infusion.

Acceleration of linear growth during puberty is associated with increased GH secretion, although the relationship between growth and GH is complex. As GH exists as a family of isoforms, some of which may not be identified by immunoassay, there may be alterations in isoform secretion during pubertal maturation that result in increased growth. The changes in serum immunoreactive and bioactive GH concentrations across pubertal maturation were determined in 30 boys, aged 6.5-19.3 yr, with idiopathic short stature or constitutional delay of adolescence. Data were grouped as follows: 1) 6 prepubertal boys with bone age 7 yr or less; 2) 5 prepubertal boys with bone age of more than 7 yr, 3) 10 boys in early puberty; 4) 9 boys with mid- to late puberty. Blood was obtained every 20 min from 2000-0800 h. An equal aliquot of each serum sample was pooled for determination of GH by bio- and immunoassays. The mean serum immunoreactive GH concentration increased from 2.1 +/- 0.3, 1.8 +/- 0.3, and 2.9 +/- 0.5 micrograms/L in groups 1, 2, and 3, respectively, to a peak of 4.6 +/- 0.7 micrograms/L in group 4 (P < 0.05 vs. groups 1-3). The mean serum GH bioactivity was 48 +/- 13 micrograms/L in group 1 and declined to 39 +/- 8 and 31 +/- 3 micrograms/L in groups 2 and 3, increasing to a maximum of 64 +/- 15 micrograms/L in group 4 (P < 0.05 vs. group 3). The ratio of bioactive to immunoreactive GH suggests that the biopotencies of secreted isoforms do not increase during pubertal maturation. The role of E2 in increasing GH secretion was characterized in 8 additional early pubertal boys. Each boy received a saline infusion from 1000-0800 h, followed 1 week later by an infusion of E2 at 4.6 nmol/m2.h. Blood was obtained every 15 min from 2200-0800 h for GH and LH and every 60 min for E2 and testosterone. An equal aliquot of each overnight serum sample was pooled for insulin-like growth factor I (IGF-I) and GH by immuno- and bioassays. The mean serum LH concentration decreased from 5.0 +/- 0.9 to 2.3 +/- 0.6 IU/L (P < 0.01), and the E2 concentration increased from 22 +/- 4 to 81 +/- 26 pmol/L (P < 0.01) during saline and E2 infusions, respectively. Mean serum GH concentrations as measured by immunoassay were similar during both infusions (6.6 +/- 1.4 vs. 9.7 +/- 2.1 micrograms/L; saline vs. E2 infusion, respectively). In contrast, the mean serum GH concentration, as measured by bioassay, decreased from 48 +/- 10 micrograms/L during saline infusion to 16 +/- 3 micrograms/L during E2 infusion (P < 0.05). The mean serum IGF-I concentration also decreased significantly from 116 +/- 17 to 93 +/- 15 micrograms/L (saline vs. E2 infusion, respectively; P < 0.05). Thus, although mean overnight serum GH concentrations increase in late puberty, whether measured by immuno- or bioassay, an acute increase in E2 produces an acute decline in serum GH bioactivity and a lesser decline in the serum IGF-I concentration. These unexpected changes indicate that E2 may affect pubertal growth and GH secretion in a complex or biphasic manner depending on the context in which it is administered.