Suppression of urinary and plasma follicle-stimulating hormone by exogenous estrogens in prepubertal and pubertal children.

Clomiphene citrate, an "anti-estrogen" with mild estrogenic properties, inhibits rather than stimulates gonadotropin excretion in prepubertal and early pubertal children. These and other data suggest that the sensitivity of the hypothalamic-pituitary "gonadostat" decreases at the onset of puberty. To test this hypothesis further, the daily excretion of urinary follicle-stimulating hormone (FSH) and luteinizing hormone (LH) was determined in 19 children (5 "short normals" and 14 with isolated human growth hormone (HGH) deficiency) who were given ethinyl estradiol (EE) 1.4-14.7 mug/m(2) per day (2-10 mug/day) for 4 to 7 days. In addition, plasma and urinary gonadotropins and plasma estrogens were serially determined in two prepubertal females(with isolated HGH deficiency) given two injections (24 h apart) of estradiol benzoate, 10 mug/kg. FSH and LH concentrations in plasma and kaolin-acetone urinary concentrates and plasma 17beta-estradiol (E(2)) and estrone (E(1)) were measured by radioimmunoassays. 2-3 mug/m(2) per day of EE significantly suppressed urinary FSH (and LH when detected in the control period) in two out of six prepubertal children, while all doses >5 mug/m(2) per day suppressed urinary gonadotropins to undetectable levels in eight prepubertal subjects. In early to midpubertal subjects. 2-10 mug/m(2) per day of EE produced a slight suppression of urinary FSH, but failed to suppress to undetectable levels. Two subjects in late puberty (stage 4) did not suppress their urinary FSH while on 7 and 8.3 mug/m(2) per day. In both subjects treated with estradiol benzoate, plasma FSH promptly decreased after the first injection. Urinary FSH was suppressed to <0.1 IU/day on day 2 and urinary and plasma gonadotropins remained suppressed for the duration of the study (3 days). Plasma E(2) and E(1) rose from prepubertal values to peak concentrations of 150 to 250 pg/ml (E(2)), and 50 and 100 pg/ml (E(1)) at approximately 36 h. We conclude that the hypothalamic-pituitary-gonadal axis is operative in the prepubertal child and that the sensitivity of the hypothalamic-pituitary center(s) which control the secretion of FSH and LH decreases at the onset of puberty in man.

Secretion of unconjugated androgens and estrogens by the normal and abnormal human testis before and after human chorionic gonadotropin.

The secretion of androgens and estrogens by normal and abnormal testes was compared by determining the concentrations of dehydroepiandrosterone (DHEA), androstenedione (Delta(4)A), testosterone (T), estrone (E(1)), and 17beta-estradiol (E(2)) in peripheral and spermatic venous plasma samples from 14 normal men and 5 men with unilateral testicular atrophy. Four normal men and one patient with unilateral atrophy of the testis were given human chorionic gonadotropin (HCG) before surgery. Plasma estrogens were determined by radioimmunoassay; plasma androgens were measured by the double-isotope dilution derivative technique. Peripheral concentrations of these steroids before and after HCG were similar in both the normal men and the patients with unilateral testicular atrophy. In normal men, the mean +/-SE spermatic venous concentrations were DHEA, 73.1+/-11.7 ng/ml; Delta(4)A, 30.7+/-7.9 ng/ml; T, 751+/-114 ng/ml; E(1), 306+/-55 pg/ml; and E(2), 1298+/-216 pg/ml. Three of four subjects with unilateral testicular atrophy had greatly diminished spermatic venous levels of androgens and estrogens. HCG treatment increased the testicular secretion of DHEA and T fivefold, Delta(4)A threefold, E(1) sixfold, and E(2) eightfold in normal men. In the single subject with an atrophic testis who received HCG, the spermatic venous concentrations of androgens and estrogens were much less than in normal men similarly treated. We conclude that: (a) E(1) is secreted by the human testis, but testicular secretion of E(1) accounts for less than 5% of E(1) production in normal men; (b) HCG stimulation produces increases in spermatic venous estrogens equal to or greater than the changes in androgens, including testosterone; and (c) strikingly decreased secretion of androgen and estrogen by unilateral atrophic human tests cannot be appreciated by analyses of peripheral steroid concentrations.

Estradiol and testosterone secretion by human, simian, and canine testes, in males with hypogonadism and in male pseudohermaphrodites with the feminizing testes syndrome.

The role of the human testis in the production of 17beta-estradiol (E(2)) was investigated by determining the concentration of E(2) and testosterone in peripheral and spermatic vein plasma samples. Specimens were obtained from eight normal men, three men with hypogonadism, and two patients with the incomplete form of the feminizing testes syndrome. For comparison, similar studies were performed in four monkeys, 10 mongrel dogs, and 4 additional dogs who were given 1000 IU of human chorionic gonadotropin/day for 5 days. Plasma E(2) was measured by radioimmunoassay utilizing sheep anti-E(2) serum preceded by ether extraction and thin layer chromatographic separation of plasma steroids. Procedural blanks, which were subtracted from all reported values were 14.1+/-0.74 (SEM) pg for deionized water and 13.1+/-0.66 pg for charcoaladsorbed pooled male plasma. Pooled male and pooled female control plasmas averaged 17+/-0.71 pg/ml and 95+/-6.9 pg/ml, respectively; individual adult male specimens ranged between 8 and 28 with a mean of 18+/-1.4 pg/ml. In the eight normal men, the mean peripheral vein E(2) concentration was 20+/-1.6 pg/ml, while the spermatic vein concentration was 50 times as great, 1049+/-57 pg/ml. All three patients with testicular abnormalities had low spermatic vein E(2) concentrations (160, 280, and 416 pg/ml). Lesser E(2) gradients were found across the simian (3-fold) and canine (approximately 12-fold) testes. Testicular testosterone gradients (human 110-, simian 10-, and canine 77-fold) were greater than the E(2) gradients in all three species. In four dogs, HCG treatment elicited a 6-fold increase in peripheral and a 9-fold increase in spermatic vein testosterone concentrations; however, peripheral and spermatic vein E(2) concentrations did not differ from control values. Spermatic vein E(2) concentrations were > 4600 and 2210 pg/ml (post-HCG) in two patients with the incomplete form of the feminizing testes syndrome. Postorchiectomy, peripheral E(2) and testosterone concentrations fell precipitously in both patients, confirming the major contribution of the testes, in this syndrome, to circulating E(2) and testosterone. These studies provide direct evidence that the human testic secretes estradiol.

Selective inhibition of follicle-stimulating hormone secretion by estradiol. Mechanism for modulation of gonadotropin responses to low dose pulses of gonadotropin-releasing hormone.

Prepubertal girls and gonadotropin-releasing hormone (GnRH)-deficient females secrete follicle-stimulating hormone (FSH) preferentially in response to intravenous GnRH. With continued pulsatile GnRH stimulation, FSH secretion is reduced when plasma estradiol (E2) is increasing. To delineate the mechanisms involved in these changing gonadotropin responses, e studied the effect of low dose (0.025 micrograms/kg) pulsatile injections of GnRH in females with varying degrees and/or duration of endogenous GnRH deficiency (idiopathic panhypopituitarism, PHP; isolated growth hormone deficiency, IGHD; isolated gonadotropin deficiency, IGD; and anorexia nervosa, AN; both at low body weight and after weight regain). In patients presumed to have the most severe GnRH deficiency (PHP), responses of both FSH and luteinizing hormone (LH) were small and delayed, and no increase in plasma estradiol occurred during the 5 d of GnRH injections. In patients previously exposed to prepubertal or adult levels of endogenous GnRH secretion (IGHD, IGD, AN at low body weight), a rapid initial FSH response occurred that subsequently declined when plasma estradiol rose to concentrations greater than 40-50 pg/ml. Prior therapy with estrogen (micronized estradiol, Estrace) abolished FSH responses but LH responses were only slightly impaired. The degree of FSH response was dependent upon the time of initiation of estrogen relative to the onset of GnRH injections. Administration of estrogen after the first GnRH injection inhibited gonadotropin responses, whereas later estrogen therapy (after 1 d of GnRH pulses) blunted the GnRH induced FSH secretion without significantly impairing the LH response. In weight-regained anorexic patients who had spontaneous pulsatile LH secretion and a mean basal plasma estradiol concentration of 53 +/- 15 pg/ml, administration of GnRH pulses did not change plasma LH and a minimal FSH response was seen. The data indicate that the pattern of gonadotropin responses to low dose GnRH injections depends upon the degree of previous exposure of the pituitary to endogenous GnRH. Furthermore, estradiol selectively inhibits FSH secretion by a direct action on the pituitary gland. This action of estradiol provides an explanation for the selective reduction in FSH responses to GnRH seen during pubertal maturation in girls and during the mid-follicular stage of the menstrual cycle.

Dissociation of lutropin-induced loss of testicular lutropin receptors and lutropin-induced desensitization of testosterone synthesis.

The relationship between changes in testicular lutropin receptors, as measured by specific binding of 125I-labeled human chorionic gonadotropin, and testosterone synthesis in response to lutropin (testicular responsiveness) was studied in intact and hypophysectomized rats. Administration of a single 200-microgram dose of ovine lutropin to intact rats results at 3 days in a 58% decrease in lutropin receptors associated with a parallel decrease in testicular responsiveness. A single 30-microgram dose of lutropin to intact rats resulted in a comparable decrease in lutropin receptors with a transient increase in testicular responsiveness. Rats receiving twice-daily injections of 15 microgram lutropin for 10 days exhibited a 48% decrease in lutropin receptors by day 3 which persisted during the 10-day treatment period, but was accompanied by a progressive increase in testicular responsiveness to lutropin. Hypophysectomy resulted in an 80% loss of receptors and a 72% loss in responsiveness 7 days after surgery. Daily treatment with lutropin initiated immediately following surgery resulted in a further dose-dependent decrease in lutropin receptors and a dose-dependent increase in testicular responsiveness. Loss of lutropin receptors was not due to occupancy of the receptor by exogenous lutropin. These studies demonstrate a dissociation between the negative regulation of lutropin receptors and testicular responsiveness to lutropin. Furthermore, the studies in hypophysectomized rats indicate that lutropin is the only hormone essential for maintenance of steroidogenesis and that this is independent of lutropin receptor concentration.

Hypocalcemia, hypomagnesemia, and transient hypoparathyroidism during therapy with potassium phosphate in diabetic ketoacidosis.

The effects of intravenous administration of potassium phosphate in the treatment of diabetic ketoacidosis were studied in nine children, ages 9 9/12 to 17 10/12 yr. During phosphate infusion (20--40 meq/L of fluid), all children maintained normal serum concentrations of phosphorus. Transient hypocalcemia occurred in six and transient hypomagnesemia in five patients. One child developed carpopedal spasms refractory to intravenous infusion of calcium gluconate but responsive to intramuscular injection of magnesium sulfate. In three patients, serum levels of intact parathyroid hormone were low at the time of hypocalcemia, an observation that suggests transient hypoparathyroidism. This study indicates that the use of potassium phosphate as the sole source of potassium replacement might potentiate ketoacidosis-induced hypocalcemia through multiple mechanisms.

A daily neural signal for luteinizing hormone release in the untreated ovariectomized rat: changes in gonadotropin-releasing hormone content of the preoptic area and hypothalamus throughout the day.

Gonadotropin-releasing hormone (GnRH) content of preoptic areas (POA) and hypothalami, and serum gonadotropins of rats ovariectomized six weeks earlier were measured throughout the day in two experiments. In the first, rats were decapitated at 2 h intervals between 0800 and 1800 h. The entire preoptic-hypothalamic region was removed and extracted for radioimmunoassay (RIA) of GnRH. Serum gonadotropins measured by RIA were highly variable but mean concentrations were not significantly different throughout the day. However, preoptic hypothalamic content of GnRH declined markedly between 1000 and 1200 h. In the second experiment, 75 rats were divided into three groups and were untreated or were implanted sc with empty Silastic capsules or capsules containing estradiol-17beta (E2). Two days later, groups of five rats from each of the three treatment groups were decapitated at 0800, 1100, 1400, 1700 and 2000 h. The preoptic area was separated from the hypothalamus by a transverse cut at the caudal aspect of the optic chiasm. POA and hypothalamic content of GnRH correlated well (r=0.74, P less than 0.001, n=75). Two-way analysis of variance failed to reveal any effect of treatment on the GnRH content in either the POA or hypothalamus. GnRH content of both regions decreased significantly between 1100 and 1700h regardless of whether E2 was administered. In striking contrast, gonadotropin surges occurred in the late afternoon only in the E2-treated rats. Serum GnRH was undetectable (less than 5 pg/ml) in all groups of animals. These experiments demonstrate that in the untreated ovariectomized rat GnRH content of the POA and hypothalamus decreases during the early afternoon. This study supports the concent of a daily neural signal for LH release and that E2 is necessary for expression of the daily LH surge in the ovariectomized rat.

Effects of prolactin on testicular regression and recrudescence in the golden hamster.

Transfer of adult male hamsters from a long to a short photoperiod causes testicular atrophy, which is accompanied by decreases in testicular LH receptors and in plasma PRL and testosterone levels. A decrease in plasma gonadotropin levels is also frequently observed. When the decline in peripheral PRL concentration is prevented by transplantation of homologous pituitary(ies) under the kidney capsule, testicular atrophy is delayed and incomplete. This appears to be due to the maintenance of testicular LH receptors by PRL secreted from the grafts and probably also to the stimulation of GSH release from the in situ pituitary. In hamsters maintained in a long photoperiod, ectopic pituitary homografts can increase testicular LH receptor levels, concentrations of testosterone and FSH in the plasma, and the weights of the testes and the seminal vesicles. In contrast to the findings obtained in rats and mice, chronic hyperprolactinemia in the male hamster does not inhibit gonadotropin release or interfere with copulatory behavior. These findings are consistent with our earlier suggestion that PRL plays an important part in the regulation of gonadal function in the male hamster but indicate that testicular atrophy in a short photoperiod cannot be explained solely by a reduction in PRL release.

Opioid and neurotransmitter regulation of pituitary gonadotropin-releasing hormone (GnRH) receptors in the ovariectomized estradiol-treated rat: role of altered GnRH secretion.

An acute transient fall in the number of pituitary GnRH receptors (GnRH-R) is observed before the preovulatory gonadotropin surge in cycling rats and before the afternoon daily gonadotropin surge in ovariectomized estradiol-treated rats. In the latter model, this fall can be reproduced by administration of the opioid antagonist naloxone, whereas the opioid agonist morphine acutely increases GnRH-R. In this study we investigated the mechanisms of this opioid effect and examined the effects of other neurotransmitter substances on modulation of pituitary GnRH-R. Administration of the dopaminergic agonists bromocriptine and L-dopa or the alpha-adrenergic receptor blocker phenoxybenzamine elevated GnRH-R acutely from average basal values of 240 +/- 22 and 254 +/- 21 fmol/mg protein to maximal values of 374 +/- 49, 441 +/- 67 and 461 +/- 75 fmol/mg, respectively, whereas the alpha-adrenergic agonist clonidine transiently decreased GnRH-R to 186 +/- 19 fmol/mg. Placement of radiofrequency lesions in the mediobasal hypothalamus or pretreatment with anti-GnRH serum completely abolished the ability of both morphine and naloxone to modulate the number of GnRH-R. These data indicate that the opioid-induced modulation of pituitary GnRH-R requires an intact hypothalamus and that both dopaminergic and alpha-adrenergic neurotransmitter systems may be involved. The final step of this action probably involves acute modulation of GnRH secretion (altered frequency and/or amplitude), which results in acute transient changes in the number of pituitary GnRH-R.

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.

Low dose pulsatile gonadotropin-releasing hormone in anorexia nervosa: a model of human pubertal development.

Patients suffering from anorexia nervosa were studied to determine whether gonadotropin-releasing hormone (GnRH) could induce the hormonal changes which occur during normal puberty. Three amenorrheic patients were studied at low body weight (less than 70% ideal BW). All three patients were prepubertal, as evidenced by immature LH and FSH responses to a standard GnRH test (2.5 micrograms/kg BW) and the absence of spontaneous LH peaks both during the day and during sleep. Low doses of GnRH (0.025--0.05 microgram/kg), aimed at producing peak plasma GnRH values of approximately 200 pg/ml, were given by iv bolus injection every 2 h for 5 days. Plasma responses of FSH, LH, and estradiol were measured by RIA. Preinjected FSH values rose rapidly to plateau (range, 15--30 mIU/ml) on the second to third day before falling despite the continued administration of GnRH. In contrast, plasma LH and estradiol increased gradually throughout the 5 days of injections. Acute FSH responses to GnRH initially exceeded those of LH but subsequently decreased, whereas LH increments increased progressively after the first 36 h of injections. The 5 days of low dose GnRH pulses induced maturation of the hormone responses to the standard GnRH test, so that LH release exceeded that of FSH at the completion of the study. These changes in the patterns of FSH and LH secretion are similar to those seen during normal puberty in girls and during the follicular phase of the menstrual cycle. The results demonstrate a changing pattern of pituitary response to physiological administration of GnRH and indicate that the changes in gonadotropin secretion during normal puberty are consistent with the effects of the single decapeptide GnRH.

LH and FSH responsiveness to intravenous gonadotropin-releasing hormone (GnRH) in children with hypothalamic or pituitary disorders: lack of effect of replacement therapy with human growth hormone.

To evaluate the diagnostic and prognostic usefulness of the GnRH test, gonadotropin responses to iv GnRH (Parke-Davis) were determined in 82 young patients (2,5 mo.-21 yr.) and 6 normal men. After extensive evaluation, 40 patients (31 boys and 9 girls) were considered "endocrinologically normal." Repeat tests were performed in 17 patients at 6-12 mo. intervals. Nine patients with presumed isolated hGH deficiency and 3 patients with multiple pituitary deficiencies were studied before and at the end of 12 mo. of hGH therapy. Serial blood samples were obtained before and after an iv bolus injection of GnRH (2.5 mug/kg, 74 tests, or 10 mug/m2, 36 tests). LH and FSH were determined by radioimmunoassay. Maximum concentration, maximum increment (deltamax), and response area were compared with degree of skeletal maturation to evaluate responses. Clinically, the most useful determination was the deltamax LH. All "normal" children with bone ages greater than 12 yr had LH responses in or slightly above the range of the values of the 6 normal men: deltamax LH, 39 +/- 8 (SE) mIU/ml; range 13-57. Severely blunted or absent responses were seen in 14/15 patients (bone ages 3 mo.-14 yr.) with multiple pituitary deficiencies. Boys with isolated hGH deficiency and bone ages of less than 10 yr had significantly lower responses than "short normal" boys with similar skeletal maturation: deltamax LH, 4.8 +/- 0.9 vs 8 +/- 1.3 mIU/ml, P is less than .05. Although the mean growth velocity of hGH-treated children increased from 3.2 to 8.9 cm/yr, LH and FSH responses were unchanged. These studies indicate that 1) children with idiopathic hypopituitarism (including those with presumed isolated hGH deficiency) have significantly decreased responsiveness to GnRH which does not respond to 6 to 12 months of hGH treatment; and 2) decreased responsiveness to GnRH in patients with bone ages of greater than 12 yr is presumptive evidence of gonadotropin deficiency.

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.

Insulin and blood pressure during weight loss in obese adolescents.

The role of insulin in the regulation of blood pressure was evaluated in 50 obese adolescents before and after a 20-week weight loss program. When compared with 10 nonobese adolescents, the obese subjects had significantly higher systolic, diastolic, and mean arterial pressures (p = 0.005), an elevated 24-hour urinary sodium excretion (p = 0.002), an elevated fasting insulin concentration (p = 0.001), and an abnormal insulin response to an oral glucose tolerance test (sum of the insulins at 0, 1, and 2 hours post-oral glucose load; p = 0.001). We also observed a significant correlation between systolic and diastolic blood pressure (age and sex normalized) and body weight (r = 0.57, p less than 0.01 and r = 0.7, p less than 0.01), fasting insulin (r = 0.49, p less than 0.01 and r = 0.54, p less than 0.01), and sum of insulins (r = 0.42, p less than 0.01 and r = 0.46, p less than 0.01). To study the effect of weight loss on the relationship between blood pressure and insulin, the obese subjects were randomly assigned to three groups: 15 to a diet and behavior change group, 18 to a diet, behavior change, and exercise group, and 17 to an obese control group. Compared with the obese control group, the two weight loss groups each experienced a significant decrease in insulin (p less than 0.01), sum of the insulins (p less than 0.01), and blood pressure (p less than 0.01). The decrease in blood pressure during the weight loss program significantly correlated with the change in both insulin and body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulsatile gonadotropin secretion during the human menstrual cycle: evidence for altered frequency of gonadotropin-releasing hormone secretion.

Pulsatile secretion of LH and FSH was examined to determine if the frequency of LH pulses, and by inference pulsatile GnRH secretion, varied during the human menstrual cycle. Blood samples were obtained at 10- or 20-min intervals for 12 or 24 h at 7-day intervals during the same ovulatory cycle in eight normal women. Ovarian steroids showed the expected cyclical changes and mean plasma FSH concentrations showed an inverse relationship to estradiol, being low when estradiol was greater than 150 pg/ml. Sampling every 10 min revealed a constant LH pulse amplitude but LH pulse frequency increased (from 11.8 to 14.3 pulses/12 h) during the follicular phase. LH pulse frequency was not further increased in two women sampled during the LH surge, but pulse amplitude was markedly higher. During the luteal phase LH pulse frequency was reduced to eight pulses/12 h but frequency was more variable between subjects than in the follicular phase. LH pulse amplitude showed striking variation (0.8-29.4 mIU/ml) during the luteal phase of the cycle and large LH secretory episodes which lasted 1-3 h were irregularly interspersed among periods of low amplitude LH secretion. These data show that the frequency of LH pulses, and by inference GnRH secretion, varies during the menstrual cycle but the degree of change is less than reported in previous studies. This observation may explain the reported efficacy of fixed frequency GnRH regimes in inducing ovulation and cyclical ovarian function.

Naloxone increases the frequency of pulsatile luteinizing hormone secretion in women with hyperprolactinemia.

The ability to change the frequency and amplitude of pulsatile GnRH secretion may be an important mechanism in maintaining regular ovulatory cycles. Hyperprolactinemia is associated with anovulation and slow frequency LH (GnRH) secretion in women. To assess whether the slow frequency of LH (GnRH) secretion is due to increased opioid activity, we examined the effect of naloxone infusions in eight amenorrheic hyperprolactinemic women (mean +/- SE, serum PRL, 160 +/- 59 micrograms/L). After a baseline period, either saline or naloxone was infused for 8 h on separate days, and LH was measured in blood obtained at 15-min intervals. Additional samples were obtained for plasma FSH, PRL, estradiol, and progesterone. Responses to exogenous GnRH were assessed at the end of the infusions. LH pulse frequency increased in all subjects from a mean of 4.0 +/- 0.5 pulses/10 h (mean +/- SE) during saline infusion to 8.0 +/- 1.0 pulses/10 h during naloxone infusion (P less than 0.01). LH pulse amplitude did not change, and mean plasma LH increased from 7.4 +/- 0.8 IU/L (+/- SE) to 11.2 +/- 1.5 IU/L during naloxone (P less than 0.01). A small but significant increase was seen in mean plasma FSH. Plasma PRL, estradiol, and progesterone were unchanged by naloxone infusion. These data suggest that elevated serum PRL reduces the frequency of LH (GnRH) secretion by increasing hypothalamic opioid activity and suggest that the anovulation in hyperprolactinemia is consequent upon persistent slow frequency LH (GnRH) secretion.

Reduction of gonadotropin-releasing hormone pulse frequency is associated with subsequent selective follicle-stimulating hormone secretion in women with polycystic ovarian disease.

Polycystic ovarian disease (PCO) is characterized by hyperandrogenism, ovulatory dysfunction, and altered gonadotropin secretion. Mean plasma FSH concentrations are low, while LH is elevated in a majority of patients. LH pulsatile secretion has been shown to occur at rapid follicular phase frequencies (approximately one pulse per h) in PCO, suggesting persistent rapid frequency GnRH secretion in this disorder. Anovulatory women with PCO were given estradiol (E2; Estraderm skin patches) and progesterone (P; vaginal suppositories) to produce midluteal concentrations for 21 days. The aim was to determine if E2 and P would slow LH (GnRH) pulse frequency and if this would result in augmented FSH secretion and follicular development after withdrawal of E2 and P. Plasma LH was measured every 10 min for 8 h before, during (days 10 and 20), and 7 days after withdrawal of E2 and P (day 28). On each of these study days FSH was measured hourly, and E2 and P were measured every 2 h. After sampling, GnRH (25 and 250 ng/kg, iv) was given to assess pituitary responsiveness. Follicular development was monitored by vaginal ultrasound through day 34 of the study. Basal LH frequency was 8.5 +/- 0.5 pulses/8 h (mean +/- SEM). During E2 and P, LH pulse frequency fell to 3.3 +/- 1.0 (10 days) and 2.3 +/- 0.8 (20 days), 39% and 27% of the basal value, respectively, and subsequently increased to 5.6 +/- 0.7 (66% of basal) 7 days after withdrawal of E2 and P. LH pulse amplitude (basal, 7.2 +/- 1.5 IU/L) was not reduced until day 20, but remained suppressed (3.9 +/- 1.1 IU/L) on day 28. As a result, mean LH (basal, 21.0 +/- 3.5 IU/L) fell progressively during E2 and P, to 3.8 +/- 1.2 IU/L on day 20, and remained low (39% of basal) 7 days after steroid withdrawal. Mean plasma FSH (basal, 7.1 +/- 0.9 IU/L) also fell during steroid administration, but in contrast to LH, had risen to 93% of the basal value by 7 days after E2 and P. LH release in response to exogenous GnRH revealed marked initial responses which did not decrease until day 20, but remained suppressed (8% of basal) after withdrawal of E2 and P. FSH responses were also suppressed on day 20, but had increased to 75% of the basal value by day 28. Initiation of follicular development occurred in all patients, and the lead follicle measured 12.3 +/- 0.8 mm 13 days post-E2 and P. Ovulation occurred in one patient.(ABSTRACT TRUNCATED AT 400 WORDS)

Connective tissue activation. XXII. A platelet growth factor (connective tissue-activating peptide-III) in human growth hormone-deficient patients.

Connective tissue-activating peptides (CTAPs) stimulate human synovial cells to exhibit a higher rate of DNA synthesis, glycolysis, and glycosaminoglycan formation. These bioactive peptides have been isolated from human platelets (CTAP-III), lymphocytes, tumor cells, and neutrophilic leukocytes. Several other growth factors, such as somatomedins A and C and nonsuppressible insulin-like activity (soluble), have been shown to be dependent on the circulating levels of pituitary GH. In this study, we examined the human GH (hGH) dependence of CTAP-III. Platelets from children with reduced or absent hGH were examined for the presence of CTAP-III. The peptide was detected qualitatively by polyacrylamide gel electrophoresis and Ouchterlony double diffusion. CTAP-III antigen, measured by RIA, was found in normal amounts in platelet lysates from normal persons and GH-deficient patients. Biological activity of the peptide was suggested by the ability of platelet lysates to stimulate the formation of glycosaminoglycans and increase sulfate incorporation into glycosaminoglycans formed in cell cultures. In addition, normal and hGH-deficient platelet lysates contained potent mitogenic activity which increased thymidine incorporation into DNA. Platelets from GH-deficient patients also released CTAP-III normally on exposure to thrombin.

Hypogonadotropic hypogonadism: hormonal responses to low dose pulsatile administration of gonadotropin-releasing hormone.

Patients with isolated gonadotropin deficiency were studied to determine whether pulsatile low dose gonadotropin-releasing hormone (GnRH) could induce the hormonal changes seen during normal puberty. Four male and two female patients with immature responses to a standard GnRH test (2.5 micrograms/kg) were given GnRH (0.025 micrograms/kg) iv every 2 h for 5 days. FSH responses varied between the sexes, and FSH concentrations in males rose continuously to 17.2 +/- 4.7 mIU/ml on day 5. In the females, FSH peaked at 13.8 and 15.8 mIU/ml on days 3-4 and then declined. The males showed increasing and the females decreasing incremental FSH responses to GnRH. LH concentrations and incremental responses to GnRH rose throughout the study in both sexes. Plasma testosterone rose slightly in the males to 0.7 +/- 0.2 ng/ml (P < 0.05), but in females estradiol increased to follicular range concentrations of 128 and 102 pg/ml. Standard GnRh tests on day 6 revealed maturation of gonadotropin responses in all patients. After termination of pulsatile GnRH, four patients were given single low dose GnRH injections on two to seven occasions over a period of 2-32 days. Initial LH responses were 2- to 14-fold greater than those seen on day 5 of pulsatile GnRH, and decreased over the next 3 weeks. FSH responses showed less initial augmentation and declined more slowly. Low dose pulsatile administration of GnRH to patients with isolated gonadotropin deficiency results in changing patterns of hormone secretion similar to those seen during puberty. Exaggerated pituitary sensitivity to GnRH may be present long after a brief period of GnRH stimulation, and may indicate previous rather than current secretion of GnRH.

Pulsatile gonadotropin secretion in women with hypothalamic amenorrhea: evidence that reduced frequency of gonadotropin-releasing hormone secretion is the mechanism of persistent anovulation.

Hypothalamic amenorrhea (HA) is a clinical disorder of unknown etiology. The diagnosis is made by exclusion of known abnormalities of pituitary and ovarian function. To determine if abnormalities of GnRH secretion could account for the anovulation and amenorrhea, we measured plasma gonadotropins every 20 min for 10- to 24-h periods in 19 women with HA. Ovarian steroids and gonadotropin responses to an iv bolus dose of GnRH (25 ng/kg) were also measured. The results were compared to those obtained during the early follicular (EF) and late luteal (LL) phases of ovulatory cycles in normal women. Plasma estradiol was lower (mean +/- SE, 52 +/- 5 pg/ml) than either cycle stage in normal women. Mean plasma LH was lower than EF values and FSH was higher than LL values. The amplitude of LH pulses in HA was similar to that in normal women. LH pulse frequency was the same as that present during the LL, but lower than that during the EF (HA, 4.7 pulses/12 h; EF, 7.7 pulses/12 h; P less than 0.05). In addition to the similar frequency, the patterns of LH secretion in HA resembled that of LL in that the amplitude of LH pulses was highly variable and pulses occurred at irregular intervals. Consistent changes in diurnal gonadotropin secretion were not found, and LH secretion was greater at night in 9 studies and during the day in 5 studies. Repeat studies in three patients (5-13 months later) revealed that LH pulse frequency was variable, being unchanged in 1, increased in 1, and decreased in the third patient. Thus, LH pulse frequency and, by inference, GnRH pulse frequency are similar in HA to those in the normal luteal phase despite a different steroid milieu. GnRH pulse frequency increases from the luteal to the follicular phases of normal cycles and may be important in the initiation of ovarian follicular maturation. These data suggest that the absence of cyclical gonadotropin secretion and anovulation in HA result from a decreased frequency and irregular amplitude of GnRH secretion and consequent absence of ovarian follicular maturation.