Testosterone, free testosterone, and free androgen index in women: Reference intervals, biological variation, and diagnostic value in polycystic ovary syndrome.

OBJECTIVE: The objective of our study was to determine reference intervals and biologic variation for testosterone (T), free testosterone (fT), and free androgen index (FAI) in women with accurate methods and to test the discriminative value of these parameters in a polycystic ovary syndrome (PCOS)-population. METHODS: Serum was obtained daily during a normal menstrual cycle from 25 healthy women (677 data-points). A single serum sample was obtained from 44 PCOS-patients. T was measured by LC­MS/MS and by Architect® 2nd generation T Immunoassay. Sex hormone-binding globulin was measured to calculate fT and FAI. Results: Reference intervals which were established in healthy women with an ovulatory menstrual cycle were T = 0.3-1.6 nmol/L and 0.5-2.0 nmol/L, fT = 5.2-26 pmol/L and 7.2-33 pmol/L, and FAI = 0.4-2.9 and 0.6-4.4, by LC-MS/MS and immunoassay, respectively. T, fT and FAI were higher in PCOS patients than in controls (p b 0.0001). The areas under the curve of receiver operator characteristic (ROC) plots were not different for T, fT, or FAI when T was measured by LC­MS/MS versus immunoassay based on prediction of PCOS. FAI and fT were the strongest predictors of PCOS. CONCLUSIONS: When based upon the appropriate reference intervals and ROC analysis, LC-MS/MS and second generation immunoassay have equivalent clinical utility for the diagnosis of PCOS.

Importance of inhibin B in the regulation of FSH secretion in the human male.

Regulation of FSH secretion in the male involves a complex balance between stimulation by GnRH from the hypothalamus, inhibitory feedback by sex steroids (T and E2) and inhibin B (Inh B) from the gonads, and autocrine/paracrine modulation by activin and follistatin within the pituitary. The aim of the present study was to delineate the feedback control of FSH in the human male with specific reference to the relative roles of sex steroids vs. Inh B. Two experimental human models were used: 1) normal (NL) men subjected to acute sex steroid withdrawal (-T, -E2, + Inh B), and 2) functional castrate males (-T, -E2, -Inh B). Nine NL men (age range, 25-45 yr) and three castrate males (age range, 23-47 yr) were studied. The NL men underwent acute sex steroid suppression using high dose ketoconazole (1-g loading dose, followed by 400 mg, orally, four times daily for 150 h). Gonadotropin secretion was characterized by frequent blood sampling every 10 min for 12 h at baseline and on d 3 and 6 of sex steroid ablation. In the three castrate subjects, blood sampling was performed every 5 min for 24 h 8 wk after discontinuing androgen replacement therapy. In the NL men, treatment with ketoconazole resulted in a decline to castrate levels in T (451 +/- 20 to 38 +/- 7 ng/dl; P < 0.0005) and E2 (39 +/- 4 to 15 +/- 2 pg/ml; P < 0.005) and a modest, but significant, decline in Inh B levels, which remained within the normal range (183 +/- 19 to 136 +/- 13 pg/ml; P < 0.005). This suppression of sex steroids was associated with a more marked increase in mean LH (9.5 +/- 0.9 to 24.9 +/- 2.0 IU/liter; P < 0.0001) than FSH levels (5.1 +/- 0.7 to 10.0 +/- 1.5 IU/liter; P < 0.005), with the latter not exceeding the normal adult male range. The castrate subjects had a mean T level of 66 +/- 8 ng/dl, an E2 level of 20 +/- 1 pg/ml, and undetectable Inh B levels. Despite a similar sex steroid milieu, the mean FSH levels observed in NL men after acute sex steroid ablation were approximately 6-fold lower than those seen in the castrate subjects (10.0 +/- 1.5 vs. 59.5 +/- 17.7 IU/liter; P < 0.0005). In contrast, mean LH levels in the NL men were less than 3-fold lower than those in castrate subjects (24.9 +/- 2.0 vs. 66.8 +/- 20.1 IU/liter; P < 0.005). From this human model of acute sex steroid withdrawal, we conclude that Inh B is likely to be the major feedback regulator of FSH secretion in the human male.

The fertile eunuch variant of idiopathic hypogonadotropic hypogonadism: spontaneous reversal associated with a homozygous mutation in the gonadotropin-releasing hormone receptor.

Mutations in the GnRH receptor (GnRH-R) gene have been reported to cause idiopathic hypogonadotropic hypogonadism (IHH). Herein, we describe a 26-yr-old male with a mild phenotypic form of IHH, the fertile eunuch syndrome (IHH in the presence of normal testicular size and some degree of spermatogenesis), associated with a homozygous mutation (Gln106Arg) in the GnRH-R. This mutation, located in the first extracellular loop of the GnRH-R, has been previously shown to decrease but not eliminate GnRH binding. The proband had hypogonadal testosterone levels, detectable but apulsatile gonadotropin secretion, and a normal adult male testicular size of 17 mL at baseline. After only 4 months of treatment with hCG alone, he developed sperm in his ejaculate and his wife conceived. Following cessation of hCG therapy, the patient demonstrated reversal of his hypogonadotropism as evidenced by normal adult male testosterone levels and the appearance of pulsatile luteinizing hormone secretion. This case thus expands the emerging clinical spectrum of GnRH-R mutations, provides the first genetic basis for the fertile eunuch variant of IHH and documents the occurrence of reversible IHH in a patient with a GnRH-R mutation.

The importance of autosomal genes in Kallmann syndrome: genotype-phenotype correlations and neuroendocrine characteristics.

Kallmann syndrome (KS) consists of congenital, isolated, idiopathic hypogonadotropic hypogonadism (IHH) and anosmia. The gene responsible for the X-linked form of KS, KAL, encodes a protein, anosmin, that plays a key role in the migration of GnRH neurons and olfactory nerves to the hypothalamus. In addition to X-linked pedigrees, autosomal dominant and recessive kindreds with KS have been reported. The relative importance of these autosomal vs. X-linked genes in producing KS, and the frequency of KAL mutations, are currently unknown because these are rare disorders and large series are unusual. We examined 101 individuals with IHH (+/- anosmia) and their families to determine their modes of inheritance, incidence of mutations in the coding sequence of KAL, genotype-phenotype correlations, and [in a subset (n = 38)] their neuroendocrine phenotype. Of the 101 patients, 59 had true KS (IHH + anosmia/hyposmia); whereas, in the remaining 42, no anosmia was evident in the patients or their families. Of the 59 KS patients, 21 were familial, whereas 38 were sporadic cases. Mutations in the coding sequence of KAL were identified in only 3 of 21 familial cases (14%) and 4 of 38 (11%) of the sporadic cases. Of the X-linked cases confirmed by mutational analysis, only 1 of 3 pedigrees appeared X-linked by inspection whereas the other 2 contained only affected brothers. Female members of known KAL mutation families (n = 3) exhibited no reproductive phenotype and were not anosmic, whereas families with anosmic women (n = 3) were not found to carry mutations in KAL. Mutations were uniformly absent in nonanosmic IHH probands (n = 42), as well as in families with both anosmic and nonanosmic members (n = 2). Overall, 4 novel mutations were identified (C172R, R191x, R457x, and delC@L600). With respect to neuroendocrine phenotype, KS men with documented KAL mutations (n = 8) had completely apulsatile LH secretion, whereas those with autosomal modes of inheritance demonstrated a more variable spectrum with evidence of enfeebled (but present) GnRH-induced LH pulses. Our conclusions are: 1) Confirmed mutations in the coding sequence of the KAL gene occur in the minority of KS cases, i.e. only 14% of familial and 11% of sporadic cases; 2) The majority of familial (and presumably sporadic) cases of KS are caused by defects in at least two autosomal genes that are currently unknown; 3) Obligate female carriers in families with KAL mutations have no discernible phenotype; 4) KAL mutations are uniformly absent in patients with either normosmic IHH or in families with both anosmic and nonanosmic individuals; and 5) Patients with KAL mutations have apulsatile LH secretion consistent with a complete absence of GnRH migration of GnRH cells into the hypothalamus, whereas evidence of present (but enfeebled) GnRH-induced LH pulses may be present in autosomal KS cases. Taken together, these findings suggest that autosomal genes account for the majority of familial cases of KS, and that unique neuroendocrine phenotypes consistent with some GnRH neuronal migration may exist in these patients.

Prevalence, phenotypic spectrum, and modes of inheritance of gonadotropin-releasing hormone receptor mutations in idiopathic hypogonadotropic hypogonadism.

Mutations in the GnRH receptor (GNRHR) have been described as a cause of reproductive failure in a subset of patients with idiopathic hypogonadotropic hypogonadism (IHH). Given the apparent rarity of these mutations, we set out to determine the frequency and distribution of GNRHR mutations in a heterogeneous population of patients with IHH who were well characterized with respect to diagnosis, phenotype, and mode of inheritance and to define their distribution within the receptor protein. One hundred and eight probands with IHH were screened for mutations in the coding sequence of GNRHR. Forty-eight of the 108 patients had a normal sense of smell, whereas the remaining 60 had anosmia or hyposmia (Kallmann syndrome). Exon segments in the GNRHR were screened for mutations using temperature gradient gel electrophoresis, and all mutations were confirmed by direct sequencing. Five unrelated probands (3 men and 2 women), all normosmic, were documented to have changes in the coding sequence of the GNRHR. Two of these probands were from a subgroup of 5 kindreds consistent with a recessive mode of inheritance, establishing a GNRHR mutation frequency of 2 of 5 (40%) in patients with normosmic, autosomal recessive IHH. The remaining 3 probands with GNRHR mutations were from a subgroup of 18 patients without evidence of familial involvement, indicating a prevalence of 3 of 18 (16.7%) in patients with sporadic IHH and a normal sense of smell. Among the five individuals bearing GNRHR mutations, a broad spectrum of phenotypes was noted, including testicular sizes in the male that varied from prepubertal to the normal adult male range. Three probands had compound heterozygous mutations, and two had homozygous mutations. Of the eight DNA sequence changes identified, four were novel: Thr(32)Ile, Cys(200)Tyr, Leu(266)Arg, and Cys(279)TYR: COS-7 cells transiently transfected with complementary DNAs encoding the human GNRHR containing each of these four novel mutations failed to respond to GnRH agonist stimulation. We conclude that 1) the spectrum of phenotypes in patients with GNRHR mutations is much broader than originally anticipated; 2) the frequency of GNRHR mutations may be more common than previously appreciated in familial cases of normosmic IHH and infrequent in sporadic cases; and 3) functional mutations of the GNRHR are distributed widely throughout the protein.

Differential regulation of gonadotropin secretion by testosterone in the human male: absence of a negative feedback effect of testosterone on follicle-stimulating hormone secretion.

Studies of sex steroid regulation of gonadotropin secretion in the human male have focused primarily on the respective site(s) of negative feedback of testosterone (T) and estradiol (E(2)). The use of pharmacological doses of sex steroids in these studies has precluded conclusions about the relative roles of T and E(2) in gonadotropin feedback. Thus, the aims of the present study were to 1) determine the relative contributions of T vs. E(2) to the sex steroid component of gonadotropin regulation, and 2) distinguish the feedback effects of T that that are direct (i.e. mediated by the androgen receptor) vs. indirect (mediated by aromatization to E(2)). Two experimental interventions were used: 1) inhibition of aromatization by a selective aromatase inhibitor to examine the impact of selective E(2) withdrawal; and 2) acute medical castration to examine the effect of ablating both T and E(2). Sixteen normal (NL) men (mean age, 30.5 +/- 2.2 yr) were studied. Nine NL subjects were treated with the aromatase inhibitor, anastrozole (10 mg, orally, daily, for 5 days). Twelve NL men underwent medical castration with ketoconazole (1-g loading dose followed by 400 mg, orally, four times a day for 5 days). Ketoconazole-treated subjects received concomitant treatment with dexamethasone (0.5 mg twice daily) to prevent the development of adrenal insufficiency. Single blood samples were drawn daily between 0800-1000 h. To ensure that dexamethasone was not altering the gonadotropin response to sex steroid ablation by a direct pituitary effect, five GnRH-deficient men (mean age, 37.6 +/- 3.9 yr) underwent GnRH dose-response studies at baseline and after treatment with dexamethasone (0.5 mg twice daily). Aromatase blockade caused significant lowering of E(2) (33 +/- 3 to 14 +/- 1 pg/mL; P: < 0.0005) with a corresponding increase in T levels (563 +/- 42 to 817 +/- 81 ng/dL; P: < 0.05). Treatment with ketoconazole resulted in equivalent suppression of E(2) (41 +/- 4 to 14 +/- 1 pg/mL; P: < 0.0005), but also induced castrate levels of T (491 +/- 28 to 40 +/- 3 ng/dL; P: < 0.0005). Both treatment regimens were associated with a significant increase in gonadotropin levels. For LH, the percent increase in serum levels after castration was almost 3-fold greater than that seen after selective E(2) withdrawal (275 +/- 23% with ketoconazole vs. 95.6 +/- 21% with anastrozole; P: < 0.005). Despite the divergent changes in T levels with these two maneuvers (a marked decrease after ketoconazole and a significant increase with anastrozole), the percent rise in FSH levels was similar in the two protocols (91 +/- 6% vs. 71 +/- 7%, respectively; P: = NS). Inhibin B levels were unchanged after selective E(2) withdrawal (156 +/- 23 vs. 176 +/- 19 pg/mL), but decreased slightly with ketoconazole (156 +/- 15 to 131 +/- 11 pg/mL; P: < 0.05). In contrast to the effects of glucocorticoid administration on gonadotropin secretion in women, no significant changes were observed in the GnRH-deficient men treated with dexamethasone in terms of mean LH levels (19.8 +/- 3.2 vs. 23.3 +/- 5.4 IU/L), mean LH pulse amplitude after GnRH (16.0 +/- 2.5 vs. 19.0 +/- 5.1 IU/L), or mean FSH levels (8.0 +/- 1.9 vs. 9.2 +/- 2.4 IU/L, pre vs. post). These studies provide evidence of differential regulation of gonadotropin secretion by T in the human male. T exerts both direct and indirect feedback on LH secretion, whereas its effects on FSH appear to be mediated largely by aromatization to E(2). From these data we conclude that in terms of sex steroid feedback, E(2) is the predominant regulator of FSH secretion in the human male.

Genetics of hypogonadotropic hypogonadism.

Determining the physiologic influences that modulate GnRH secretion, the prime initiator of reproductive function in the human, is fundamental not only to our understanding of the rare condition of congenital idiopathic hypogonadotropic hypogonadism (IHH), but also common disorders such as constitutional delay of puberty and hypothalamic amenorrhea. IHH is characterized by low levels of sex steroids and gonadotropins, normal findings on radiographic imaging of the hypothalamic-pituitary regions, and normal baseline and reserve testing of the remainder of the hypothalamic-pituitary axes. Failure of the normal pattern of episodic GnRH secretion results in delay of puberty and infertility. IHH is characterized by rich clinical and genetic heterogeneity, variable modes of inheritance, and association with other anomalies. To date, 4 genes have been identified as causes of IHH in the human; KAL [the gene for X-linked Kallmann syndrome (IHH and anosmia)], DAX1 [the gene for X-linked adrenal hypoplasia congenita (IHH and adrenal insufficiency)], GNRHR (the GnRH receptor), and PC1 (the gene for prohormone convertase 1, causing a syndrome of IHH and defects in prohormone processing). As these mutations account for less than 20% of all IHH cases, discovery of additional gene mutations will continue to advance our understanding of this intriguing syndrome.

Aromatase inhibition in the human male reveals a hypothalamic site of estrogen feedback.

The preponderance of evidence states that, in adult men, estradiol (E2) inhibits LH secretion by decreasing pulse amplitude and responsiveness to GnRH consistent with a pituitary site of action. However, this conclusion is based on studies that employed pharmacologic doses of sex steroids, used nonselective aromatase inhibitors, and/or were performed in normal (NL) men, a model in which endogenous counterregulatory adaptations to physiologic perturbations confound interpretation of the results. In addition, studies in which estrogen antagonists were administered to NL men demonstrated an increase in LH pulse frequency, suggesting a potential additional hypothalamic site of E2 feedback. To reconcile these conflicting data, we used a selective aromatase inhibitor, anastrozole, to examine the impact of E2 suppression on the hypothalamic-pituitary axis in the male. Parallel studies of NL men and men with idiopathic hypogonadotropic hypogonadism (IHH), whose pituitary-gonadal axis had been normalized with long-term GnRH therapy, were performed to permit precise localization of the site of E2 feedback. In this so-called tandem model, a hypothalamic site of action of sex steroids can thus be inferred whenever there is a difference in the gonadotropin responses of NL and IHH men to alterations in their sex steroid milieu. A selective GnRH antagonist was also used to provide a semiquantitative estimate of endogenous GnRH secretion before and after E2 suppression. Fourteen NL men and seven IHH men were studied. In Exp 1, nine NL and seven IHH men received anastrozole (10 mg/day po x 7 days). Blood samples were drawn daily between 0800 and 1000 h in the NL men and immediately before a GnRH bolus dose in the IHH men. In Exp 2, blood was drawn (every 10 min x 12 h) from nine NL men at baseline and on day 7 of anastrozole. In a subset of five NL men, 5 microg/kg of the Nal-Glu GnRH antagonist was administered on completion of frequent blood sampling, then sampling continued every 20 min for a further 8 h. Anastrozole suppressed E2 equivalently in the NL (136 +/- 10 to 52 +/-2 pmol/L, P < 0.005) and IHH men (118 +/- 23 to 60 +/- 5 pmol/L, P < 0.005). Testosterone levels rose significantly (P < 0.005), with a mean increase of 53 +/- 6% in NL vs. 56 +/- 7% in IHH men. Despite these similar changes in sex steroids, the increase in gonadotropins was greater in NL than in IHH men (100 +/- 9 vs. 58 +/- 6% for LH, P = 0.07; and 85 +/- 6 vs. 41 +/- 4% for FSH, P < 0.002). Frequent sampling studies in the NL men demonstrated that this rise in mean LH levels, after aromatase blockade, reflected an increase in both LH pulse frequency (10.2 +/- 0.9 to 14.0 +/- 1.0 pulses/24 h, P < 0.05) and pulse amplitude (5.7 +/- 0.7 to 8.4 +/- 0.7 IU/L, P < 0.001). Percent LH inhibition after acute GnRH receptor blockade was similar at baseline and after E2 suppression (69.2 +/- 2.4 vs. 70 +/- 1.9%), suggesting that there was no change in the quantity of endogenous GnRH secreted. From these data, we conclude that in the human male, estrogen has dual sites of negative feedback, acting at the hypothalamus to decrease GnRH pulse frequency and at the pituitary to decrease responsiveness to GnRH.

Free alpha-subunit is superior to luteinizing hormone as a marker of gonadotropin-releasing hormone despite desensitization at fast pulse frequencies.

A pulsatile pattern of GnRH stimulation is essential for normal secretion of luteinizing hormone (LH), while both continuous and fast-frequency GnRH stimulation result in a paradoxical decrease in gonadotrope responsiveness known as desensitization. Under physiological conditions there is striking concordance between the pulsatile secretion of LH and the glycoprotein free alpha-subunit (FAS). The aims of this study were to determine whether the FAS response to GnRH is also decreased at fast frequencies of GnRH stimulation and whether FAS is superior to LH as a marker of GnRH secretory activity at fast-pulse frequencies. The model of GnRH-deficient men was chosen to permit precise control of the dose and frequency of GnRH stimulation of the gonadotrope. The frequency of i.v. administration of GnRH to 5 GnRH-deficient men was progressively increased from every 120 to every 60 min, from 60 to 30 min, and from 30 to 15 min during three 12-h admissions, 1 week apart. The bolus dose of GnRH remained constant and was set at that dose previously shown to produce physiological concentrations and amplitudes of LH secretion and normal testosterone levels. As the frequency of GnRH stimulation was increased, a progressive rise in mean FAS levels was noted (353 +/- 13, 448 +/- 42, 466 +/- 50, and 698 +/- 85 ng/L [mean +/- SEM] for 120, 60, 30, and 15 min intervals; P < 0.005). However, normalization of mean FAS levels to account for the increase in total GnRH delivered with increasing frequencies revealed a progressive decrease in pituitary responsiveness to each GnRH bolus with increasing frequency of stimulation (353 +/- 13, 224 +/- 21, 117 +/- 13, 87 +/- 11 ng/L; P < 0.001). The decrease in normalized mean levels was supported by a decrease in the FAS pulse amplitude with increasing frequency (517 +/- 53, 365 +/- 50, 176 +/- 29 ng/L for 120, 60, and 30 min intervals, respectively; P < 0.005). At interpulse intervals of 120 and 60 min, there was complete concordance of LH and FAS pulses in response to GnRH. However, at the 30-min frequency FAS proved to be a better marker of GnRH with a higher true positive rate and lower number of false positives than LH (P < 0.05). At all frequencies, the number of false positive pulses detected tended to be lower for FAS than for LH (P = 0.06). From these data we conclude that FAS is subject to desensitization in response to increasing frequencies of GnRH administration in GnRH-deficient men, but is superior to LH as a surrogate marker of GnRH pulse generator activity at fast pulse frequencies.

Gender difference in the response of growth hormone (GH)-deficient adults to GH therapy.

While individual hypopituitary patients undoubtedly benefit from growth hormone (GH) therapy, there is considerable variability in the response to treatment. Given the expense, possible lack of benefit, and potential risks associated with long-term therapy, we sought to identify characteristics potentially associated with a favorable response to GH replacement. Twelve GH-deficient adults (seven men and five women aged 35.4+/-2.5 years, mean +/- SEM) participated in a 12-month open study of GH replacement (0.125 IU/kg/wk for 4 weeks and 0.25 IU/kg/wk thereafter) designed to examine the impact of GH on body composition, lipid profile, and psychological well-being. Using bioelectrical impedance analysis (BIA), there was a reduction in body fat (BF) and an increase in lean body mass (LBM) and total body water (TBW) (P < .05) following 12 months of GH treatment. In addition, there was a significant improvement in psychological well-being as indicated by a decrease in the Nottingham Health Profile (NHP) score (P < .05) and a decrease in both total cholesterol (P = .005) and low-density lipoprotein (LDL) cholesterol (P < .03). GH therapy was associated with an increase in fasting plasma glucose (P = .008) and hemoglobin A1c (HbA1c (P = .06). When analyzed by gender, the beneficial effect of GH was greater in men versus women for the increment in insulin-like growth factor-1 ([IGF-1] 375+/-59 v 148+/-73 microg/L, mean +/- SEM), increase in LBM (6.8+/-2.5 v -0.06+/-1.6 kg), reduction in BF (5.6+/-1.6 v 1.0+/-1.9 kg), and increase in TBW (5.0+/-1.6 v 0.14+/-1.29 L) (P < .05). HbA1c increased significantly in women (P < .05). The beneficial effect of GH tended to be greatest in those with the most significant abnormality in baseline values (P < .05). The duration of hypopituitarism showed an indirect correlation with the change in total cholesterol (P < .005). Baseline IGF-1 levels correlated directly with changes in TBW (P < .05). These data indicate that men with GH deficiency appear more responsive to GH therapy than women with respect to the increase in IGF-1 levels and improvement in body composition. In general, patients with the most significant abnormality in baseline values, the highest IGF-1 levels, and the shortest duration of hypopituitarism respond best. With long-term GH therapy, careful monitoring of glucose tolerance is indicated.

Insights into hypothalamic-pituitary dysfunction in polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is characterized by menstrual dysfunction and hyperandrogenism in the absence of other known causes. While the pathogenesis of PCOS remains elusive and is likely to involve abnormalities in several systems, there has long been an association of abnormal gonadotropin secretion with this disorder. In recent studies we have determined that 94% of women meeting the broad criteria for PCOS have an increased LH/FSH ratio. Several lines of evidence suggest that the mechanisms underlying the increased LH/FSH ratio in PCOS include an increased frequency of GnRH secretion. Decreased sensitivity to progesterone negative feedback on the GnRH pulse generator may play a role in this neuroendocrine defect. Additional factors which may contribute to the low to normal FSH levels in the face of increased LH include chronic mild estrogen increases and possibly inhibin. In addition to these effects on the differential control of FSH, there is increased pituitary sensitivity of LH secretion to GnRH. Both estrogen and androgens have been proposed as candidates mediating these effects. Superimposed on these underlying abnormalities in gonadotropin secretion is a marked inhibitory effect of obesity on LH secretion which may be mediated at either a pituitary or hypothalamic level.

Use of a gonadotropin-releasing hormone antagonist as a physiologic probe in polycystic ovary syndrome: assessment of neuroendocrine and androgen dynamics.

The majority of patients with polycystic ovary syndrome (PCOS) exhibit an increase in both the frequency and amplitude of LH secretion, which is thought to contribute to the hyperandrogenism associated with this disorder. The increase in LH pulse amplitude may reflect either enhanced pituitary sensitivity to GnRH and/or an increase in hypothalamic GnRH secretion. To determine whether endogenous GnRH secretion is increased in PCOS and to document the degree and time course of androgen suppression after acute LH inhibition, the Nal-Glu GnRH antagonist was administered s.c. at 4 doses (5, 15, 50, and 150 micrograms/kg) to 11 women with PCOS. The response to GnRH receptor blockade was compared with data from regularly cycling women (n = 50) studied in the early and late follicular, and early luteal phases. The response to more prolonged GnRH receptor blockade was determined in a subset of patients, in whom 150 micrograms/kg of the GnRH antagonist was administered s.c. every 24 h for 3 days (n = 7) and continued for 7 days in 3 subjects. LH levels decreased in a dose-dependent fashion after administration of the GnRH antagonist (P < 0.0001), with a maximum percent inhibition of 83 +/- 2%. At all except the 5 micrograms/kg dose, mean LH levels remained significantly lower than baseline for up to 20 h post antagonist (P < 0.002). At all antagonist doses, both the degree and duration of LH suppression were similar in PCOS and normal women. The maximum percent inhibition of FSH was 39 +/- 2%, which was significantly less than that of LH (P < 0.001). Testosterone (T) levels fell significantly within 4 h of antagonist administration, with maximum percent inhibition of 39 +/- 3% occurring at 8 h. In the patients in whom 150 micrograms/kg of the antagonist was given for 3-7 days, no further suppression of either gonadotropins or T was noted. Our conclusions were: 1) The equivalent susceptibility of LH to submaximal GnRH receptor blockade in normal and PCOS women suggests that the elevated LH levels in PCOS are not the result of an increase in the quantity of GnRH secreted. These data imply that it is the frequency of GnRH stimulation per se and/or enhanced pituitary sensitivity to endogenous GnRH that underlie the gonadotropin abnormalities in PCOS; and 2) The rapid suppression of T with increasing GnRH antagonist dose is consistent with acute regulation of T secretion by LH.

Clinical review 96: Differential control of gonadotropin secretion in the human: endocrine role of inhibin.

Although considerable strides have been made in charting the physiology and pathophysiology of inhibin in the human, further progress awaits the development of recombinant inhibin suitable for administration in human studies. Measurements of total serum inhibin, although inadequate to chart the dynamic changes associated with normal and disordered pituitary-gonadal function, have proven to be of value as indices of ovarian tumor activity. Although the roles of specific dimeric inhibin measurements in clinical practice have not been clearly established, advances in our understanding of inhibin physiology and pathophysiology in the human suggest that inhibin B may have value as a marker of Sertoli cell function in men with infertility and as a prognostic indicator in women undergoing ovulation induction therapy.

Gonadotropin pulsations across development.

Initiation and maintenance of the reproductive axis in the human is contingent upon the pulsatile secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. In man, tracking endogenous GnRH secretion relies on frequent peripheral sampling of three glycoprotein products of the gonadotrope, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and free alpha-subunit (FAS). FAS is superior to LH as a surrogate marker of GnRH secretory dynamics in those circumstances where GnRH secretion is rapid or where the pituitary LH response is low. The pattern of GnRH secretion is constantly changing across development; from high levels during the neonatal period, through a period of quiescence in mid-childhood, followed by sleep-entrained reactivation of the reproductive axis at the onset of puberty, ultimately culminating in the adult pattern of pulsatile secretion which in the male is approximately every 2 h and in the female varies with the stage of the menstrual cycle. This episodic mode of secretion allows differential impact of feedback mechanisms on the GnRH neurons and facilitates the maintenance of the reproductive axis during periods of stress by allowing frequency and amplitude modulations.

Hypogonadotropic hypogonadism.

This article outlines the changing pattern of gonadotropin-releasing hormone (GnRH)-induced gonadotropin secretion across sexual development, a knowledge of which is critical to understanding GnRH secretion in pathologic states such as hypogonadotropic hypogonadism. The clinical presentation, differential diagnosis, and treatment of hypogonadotropic hypogonadism in humans are discussed. Particular emphasis is placed on the contribution of frequent sampling studies of gonadotropin secretion and genetic studies to understanding the pathophysiology and clinical heterogeneity of isolated GnRH deficiency in humans.

Virilization in a postmenopausal woman as a result of hilus cell hyperplasia associated with a simple ovarian cyst.

A 68-year-old woman who had virilization was found to have an androgen-secreting simple ovarian cyst at laparotomy. Histologic examination demonstrated hilus cell hyperplasia in the ovarian hilus and cyst wall. In the differential diagnosis of postmenopausal virilization, hilus cell hyperplasia, although rare, should be considered.

Effects of nifedipine treatment on the renin-angiotensin-aldosterone axis.

Nifedipine is a commonly used agent in treating hypertension and angina because of its vasodilator properties. An inhibitory role of nifedipine on aldosterone (Aldo) biosynthesis has been documented in in vitro studies. This study was designed to examine the impact of a sustained release nifedipine formulation on Aldo biosynthesis and its clinical consequences. Early and late effects of nifedipine on Aldo, PRA, and Aldo/PRA ratio levels were studied in a single blind, placebo-controlled, 10-day pilot study. Ten normotensive subjects and 10 patients with hypertension were studied. Blood samples for the measurement of Aldo and PRA were obtained at 2-h intervals for 10 h on a control day and on days 1 and 8 of nifedipine treatment for the determination of baseline, early, and late values. Placebo was administered at 0800 h on the first and second days of the study, whereas nifedipine (60 mg/day) was given for the following 8 days. The Aldo/ PRA ratio was used as a sensitive indirect index of the responsiveness of Aldo secretion to adrenal stimulation with angiotensin. Compared to those on the control day, a significant rise in the integrated PRA levels occurred on the first day of nifedipine treatment, with a further rise observed on the eighth day of the treatment in the normotensive subjects (1.1 +/- 0.6, 1.7 +/- 1.2, and 2.5 +/- 1.8 ng/mL.h on the control day and the first and eighth days of treatment, respectively; P < 0.05) and by the eighth day in the hypertensive subjects (2.2 +/- 2.8 and 4.0 +/- 4.1 ng/mL.h; P < 0.05). A significant rise in integrated Aldo levels occurred in the normotensive subjects on the eighth day of nifedipine treatment (control day, 319 +/- 187; eighth day of nifedipine, 363 +/- 167 pmol/L; P < 0.05) and in the hypertensive subjects (426 +/- 219 and 535 +/- 284 pmol/L; P < 0.05). This was associated with a significant lowering of the Aldo/PRA ratio on the first day of the treatment, with further lowering on the eighth day in the normotensive (435 +/- 454, 269 +/- 209, and 182 +/- 107; P < 0.05) and by the eighth day in the hypertensive subjects (716 +/- 833 and 305 +/- 315; P < 0.05). When individual time points were examined in the normotensive subjects, Aldo/PRA levels were significantly lower on day 8 of nifedipine treatment at 1000, 1200, and 1400 h than corresponding values on the control day. The fall in the Aldo/PRA ratio during nifedipine treatment indicates that the previously reported in vitro inhibition of Aldo biosynthesis in adrenal cells is reproduced in vivo. In the absence of nifedipine, it is likely that Aldo levels would be higher for any given level of PRA. It is probable that the Aldo inhibition and the vasodilatatory effect of nifedipine combine to bring about the lowering of blood pressure. Drugs that inhibit renin-angiotensin axis activity are likely to be particularly effective when additional lowering of blood pressure is required.