How does treatment influence endocrine mechanisms in acute severe heart failure? Effects on cardiac natriuretic peptides, the renin system, neuropeptide Y and catecholamines

Inhibin B is a marker of spermatogenesis and Sertoli cell function. The objective of this study was to evaluate the biologic significance of inhibins in subfertile men and the usefulness of inhibin B for the detection of male reproductive dysfunction. Forty-seven subfertile men were evaluated by semen analysis and clinical examination. In addition to semen analysis and hormone determinations, inhibins A and B (Serotec) in all 47 and inhibin A in 25 of these samples using another kit (Biosource) were measured. Higher inhibin B (median, range: 160.3, 81.8-328.5 pg/mL vs. 94.9, 15.6-389.7 pg/mL, P = 0.024) and lower FSH (P = 0.001) were detected in men with sperm concentrations > or =20 million/mL (n = 9), compared to oligozoospermia (sperm concentration <20 million/mL, n = 38). Inhibin B correlated significantly negatively with FSH, LH, and E2, and patient's age and positively with sperm concentration, testicular volume, and TSH. Multiple regression analysis indicated FSH, LH, E2, TSH, and age as the independent variables for inhibin B with a coefficient of determination (R) of 0.53. Simultaneous measurement of both FSH and inhibin B identified more cases with oligozoospermia than either hormone alone. Taking into account the body mass index, the age of the patient, and the indirect mixed antiglobin reaction (MAR) test result in addition to FSH and inhibin B led to the correct semen classification in 45 out of 47 cases. The simultaneous measurement of FSH and inhibin B, taking into account age, body mass index, and the indirect MAR test result appears accurate in identifying subfertility. Inhibin A is detectable in some subfertile men but its significance is not clear.     

Serum inhibin B in healthy pubertal and adolescent boys: relation to age, stage of puberty, and follicle-stimulating hormone, luteinizing hormone, testosterone, and estradiol levels

Inhibin B levels were measured in serum from 400 healthy Danish prepubertal, pubertal, and adolescent males, aged 6-20 yr, in a cross-sectional study using a recently developed immunoassay that is specific for inhibin B, the physiologically important inhibin form in men. In addition, serum levels of FSH, LH, testosterone, and estradiol levels were measured. Serum levels of inhibin B, FSH, LH, testosterone, and estradiol all increased significantly between stages I and II of puberty. From stage II of puberty the inhibin B level was relatively constant, whereas the FSH level continued to increase between stages II and III. From stage III of puberty the FSH level was also relatively constant, although there was a nonsignificant trend of slightly decreased FSH levels at pubertal stage V compared to stage IV. The levels of serum LH, testosterone, and estradiol increased progressively throughout puberty. In prepubertal boys younger than 9 yr, there were no correlation between inhibin B and the other three hormones. In prepubertal boys older than 9 yr, a significant positive correlation was observed between inhibin B and FSH, LH, and testosterone. However, at this pubertal stage, each hormone correlated strongly with age, and when the effect of age was taken into account, only the partial correlation between inhibin B and LH/testosterone remained statistically significant. At stage II of puberty, the positive partial correlation between inhibin B and LH/testosterone was still present. At stage III of puberty, an negative partial correlation between inhibin B and FSH, LH, and estradiol was present, whereas no correlation between inhibin B and testosterone could be observed from stage III onward. The negative correlation between inhibin B and FSH persisted from stage III of puberty onward, whereas the correlation between inhibin B and LH and between inhibin B and estradiol was nonsignificant at stages IV and V of puberty. In conclusion, in boys, serum inhibin B levels increase early in puberty; by pubertal stage II the adult level of inhibin B has been reached. The correlation of inhibin B to FSH, LH, and testosterone changes during pubertal development. Early puberty is characterized by a positive correlation between inhibin B and LH/testosterone, but no correlation to FSH. Late puberty (from stage III) is characterized by a negative correlation between inhibin B and FSH (which is maintained in adult men), a diminishing negative correlation between inhibin B and LH, and no correlation between inhibin B and testosterone, suggesting that developmental and maturational processes in the hypothalamic-pituitary-gonadal axis take place, leading to the establishment of the closed loop feedback regulation system operating in adult men. The positive correlation between inhibin B and LH/ testosterone at the time when serum inhibin B levels rise early in puberty suggests that Leydig cell factors may play an important role in the maturation and stimulation of Sertoli cells in the beginning of pubertal development.     

Effects of chemotherapy-induced testicular damage on inhibin, gonadotropin, and testosterone secretion: a prospective longitudinal study

To investigate the role of inhibin in the control of follicle-stimulating hormone (FSH) secretion, we have measured levels of immunoreactive inhibin (ir-inhibin), inhibin B, Pro-alpha C containing inhibins, FSH, luteinizing hormone (LH), and testosterone in twelve men with hematological malignancies before, during, and after chemotherapy. Inhibin B levels fell significantly by 1 month from a mean +/- SE baseline level of 273.2 +/- 32.8 pg/mL, reaching a nadir of 52.6 +/- 15.3 pg/mL at 4 months (P < 0.0001). FSH levels increased within the first month from a baseline level of 3.9 +/- 0.6 IU/L, reaching a peak level of 22.4 +/- 3.3 IU/L at 4 months (P < 0.0001). FSH and inhibin B were significantly and inversely correlated (r = 0.69, P < 0.0001). Pro-alpha C containing inhibin levels increased significantly (P < 0.05) at 3 months and were significantly and positively correlated with FSH (r = 0.38, P = 0.002). LH levels increased significantly but to a much lesser extent than FSH, the increase becoming evident only 4 months after treatment commenced (P < 0.03). Levels of ir-inhibin and testosterone remained unchanged throughout the study. These data provide strong support to the hypothesis that inhibin B is the physiologically important form of inhibin in men, negatively regulating FSH secretion at the pituitary. Furthermore, they suggest that FSH stimulates inhibin alpha-subunit secretion by the testis.     

Serum inhibin B as a marker of spermatogenesis

Inhibin B is produced by Sertoli cells, provides negative feedback on FSH secretion, and may prove to be an important marker for the functioning of seminiferous tubules. The purpose of the present study was to examine the relationship between the spermatogenic function of the testis of subfertile men and the plasma concentrations of inhibin B and FSH. These parameters were estimated in a group of 218 subfertile men. Serum inhibin B levels were closely correlated with the serum FSH levels (r = -0.78, P < 0.001), confirming the role of inhibin B as feedback signal for FSH production. The spermatogenic function of the testis was evaluated by determining testicular volume and total sperm count. Inhibin B levels were significantly correlated with the total sperm count and testicular volume (r = 0.54 and r = 0.63, respectively; P < 0.001). Testicular biopsies were obtained in 22 of these men. Inhibin B was significantly correlated with the biopsy score (r = 0.76, P < 0.001). Receiver operating characteristic analysis revealed a diagnostic accuracy of 95% for differentiating competent from impaired spermatogenesis for inhibin B, whereas for FSH, a value of 80% was found. We conclude that inhibin B is the best available endocrine marker of spermatogenesis in subfertile men.     

Different roles of prepubertal and postpubertal germ cells and Sertoli cells in the regulation of serum inhibin B levels

To elucidate the role of germ cells in the regulation of inhibin B secretion, serum inhibin B levels in prepubertal boys and adult men whom had a concurrent testicular biopsy showing either normal or impaired testicular function were compared. In addition, by immunohistochemistry the cellular localization of the two subunits of inhibin B (alpha and betaB) were examined in adult testicular tissue with normal spermatogenesis, spermatogenic arrest, or Sertoli cell only tubules (SCO) as well as in normal testicular tissue from an infant and a prepubertal boy. Adult men with testicular biopsy showing normal spermatogenesis (n=8) or spermatogenic arrest (n=5) had median inhibin B levels of 148 pg/mL (range, 37-463 pg/mL) and 68 pg/mL (range, 29-186 pg/mL), respectively, corresponding to normal or near-normal levels of our reference population (165 and 31-443 pg/mL; n=358). Men with SCO (n=9) had undetectable or barely detectable (n=1) serum levels of inhibin B. In contrast to adults, prepubertal boys with SCO (n=12) all had measurable serum inhibin B levels that corresponded to our previously determined normal range in healthy prepubertal boys (n=114). However, in postpubertal samples from the same SCO boys, inhibin B levels were undetectable as in the adult SCO men. Intense inhibin alpha-subunit immunostaining was evident in Sertoli cells in both prepubertal and adult testes. In the prepubertal testis, positive immunostaining for the betaB-subunit was observed in Sertoli cells. In the adult testis, intense immunostaining for the betaB-subunit was evident in germ cells from the pachytene spermatocyte to early spermatid stages and to a lesser degree in Leydig cells, but not in Sertoli cells or other stages of germ cells. Thus, surprisingly, in adult men the two subunits constituting inhibin B were expressed by different cell types. We speculate that during puberty Sertoli cell maturation induces a change in inhibin subunit expression. Thus, immature Sertoli cells express both alpha and betaB inhibin subunits, whereas fully differentiated Sertoli cells only express the alpha-subunit. The correlation in adult men between serum inhibin B levels and spermatogenesis may be due to the fact that inhibin B in adult men is possibly a joint product of Sertoli cells and germ cells, including the stages from pachytene spermatocytes to early spermatids.     

Active transforming growth factor-beta in wound repair: determination using a new assay

The increase in serum FSH that accompanies female reproductive aging occurs before changes in estradiol (E2). A decrease in negative feedback from inhibin A (a product of the dominant follicle and corpus luteum) and/or inhibin B (secreted by developing follicles) may explain the rise in FSH with age. To test the hypothesis that decreases in inhibin A or inhibin B occur at an age at which the first increase in follicular phase FSH is evident, daily blood samples were obtained across the menstrual cycle from younger (<35 yr; n = 23) and older (35-46 yr; n = 21) cycling women. These cross-sectional studies were complemented by longitudinal data in 3 women studied at a 10-yr interval. In the early follicular phase, mean inhibin B was lower in older cycling women (88 +/- 7 vs. 112 +/- 10 pg/mL; P < 0.05) and FSH was higher (13.0 +/- 0.5 vs. 11.2 +/- 0.7 IU/L in older vs. younger, respectively; P < 0.04). In the mid- and late follicular phases, inhibin B was also lower in the older women (117 +/- 9 vs. 146 +/- 10 and 85 +/- 8 vs. 117 +/- 11 pg/mL; P < 0.04), whereas E2 was higher (105 +/- 14 vs. 68 +/- 5 and 240 +/- 27 vs. 163 +/- 9 pg/mL; P < 0.02), and no differences in FSH were observed in the two groups at these times. In women studied longitudinally, FSH and inhibin B varied inversely in the follicular phase. In the early luteal phase, mean inhibin B was lower in the older group (64 +/- 6 vs. 94 +/- 12 pg/mL; P < 0.03), and FSH was higher (12.5 +/- 1.0 vs. 9.7 +/- 0.6 IU/L; P < 0.03). In the mid- and late luteal phases, inhibin B was also lower in older subjects (21 +/- 2 vs. 33 +/- 5 and 22 +/- 2 vs. 36 +/- 6 pg/mL; P < 0.02). No difference in inhibin A, E2, or progesterone was observed across the luteal phase, between the two groups. However, in all subjects studied longitudinally, increased age was associated with a decrease in inhibin A, inhibin B, and progesterone in the absence of changes in E2. Our conclusions were: 1) reproductive aging is accompanied by decreases in both inhibin B and inhibin A; 2) the decrease in inhibin B precedes the decrease in inhibin A and occurs in concert with an increase in E2, suggesting that inhibin B negative feedback is the most important factor controlling the earliest increase in FSH with aging; 3) these studies suggest that the decrease in inhibin B is the earliest marker of the decline in follicle number across reproductive aging.     

Gonadotropic control of secretion of dimeric inhibins and activin A by human granulosa-luteal cells in vitro

PURPOSE: It is well established that human granulosa cells and luteal cells express inhibin/activin subunit protein and secrete immunoreactive inhibin. The gonadotropic control of secretion of different molecular forms of inhibin and activin A by granulosa-luteal cells (G-LCs) was investigated using recently developed specific enzyme immunoassays (EIAs). METHODS: Granulosa-luteal cells obtained at IVF egg pickup were cultured in a serum-free medium at 37 degrees C in a water-saturated incubator with 5% CO2 for up to 5 days. Experiments with varying concentrations of human FSH, hLH, and hCG were carried out. RESULTS: FSH raised the secretion of inhibin A and pro-alpha C-containing inhibins after 24 and 48 hr in culture. Inhibin B was raised after 24 hr and activin A was raised after 48 hr of FSH treatment. LH treatment for 24 hr stimulated inhibin A, inhibin B, pro-alpha C, and activin A. hCG stimulated G-LC secretion of inhibin A after 48 hr and pro-alpha C after 24 hr. Paradoxically, inhibin B secretion was inhibited by 1 and 10 ng/ml hCG after 48 hr. Activin A was stimulated by hCG after 24 and 48 hr of incubation. G-LC secretion of estradiol and progesterone was also stimulated significantly by LH and hCG. CONCLUSIONS: Secretion of dimeric inhibins and activin A is controlled differentially by gonadotropins.     

Inhibin B in men with normal and disturbed spermatogenesis

Inhibin, a dimeric gonadal glycoprotein, inhibits the production and/or secretion of follicle stimulating hormone (FSH). The major species currently recognized are inhibin A (alphabeta A subunit) and inhibin B (alphabeta B subunit). In men, inhibin B seems to be the physiologically important form of inhibin. Therefore we measured serum inhibin B using a new two-site immunoenzymatic assay in 14 men (mean +/- SEM age, 34.5 +/- 0.7 years) with sperm counts >20 x 10(6)/ ml, in 35 men (mean +/- SEM age, 36.4 +/- 1.3 years) with oligozoospermia (sperm count <20 x 10(6)/ml) and in men with azoospermia (three orchidectomized men, three men with Klinefelter's syndrome, 10 men with Kallmann's syndrome). We compared inhibin B concentrations with serum FSH and sperm concentrations. In men with normal sperm concentrations (44.7 +/- 6.4 x 10(6)/ml), the concentration of inhibin was 223 +/- 18 pg/ml and of FSH 5.0 +/- 0.7 IU/l; in patients with low sperm concentrations (3.7 +/- 0.8 x 10(6)/ml), the concentration of inhibin B was 107 +/- 12 pg/ml and of FSH 12.2 +/- 1.5 IU/l. In all patients, except those with hypogonadotrophic hypogonadism, the relationship between inhibin B and FSH concentrations was inverse (r = -0.69, P < 0.0001). In all patients the sperm concentration was positively correlated with inhibin B concentrations (r = 0.70, P < 0.0001) and negatively correlated with FSH concentrations (r = -0.37, P < 0.01). We conclude that inhibin B may be a marker of exocrine testicular function and could offer improved diagnosis and treatment modalities for male infertility.     

Ontogeny of gonadotropin, testosterone, and inhibin secretion in normal boys through puberty based on overnight serial sampling

To investigate hormonal changes occurring in male puberty, we measured LH, FSH, testosterone, and alpha-inhibin immunoactivity in serum samples drawn every 10 min for 8 h (2100-0500 h) from each of 50 normal prepubertal and pubertal boys, aged 8.4-18.8 yr. We measured gonadotropins with ultrasensitive immunofluorometric assays, and testosterone and alpha-inhibin with RIAs. Unlike previous studies, which indexed pubertal development with Tanner stages, we used testicular volume, a more finely graduated indicator of development, to reveal patterns that were obscured when subjects were grouped by Tanner stage. The overnight mean concentration of each hormone increased with testis volume, but the rate of increase on a logarithmic scale slowed as testes grew. Log LH rose precipitously in the late prepubertal and early pubertal periods and plateaued during mid- and late puberty. Based on fitted regression curves, LH increased about 20-fold (from 0.11 IU/L) between testis volumes of 1 and 10 mL, but only an additional 1.5-fold by 30 mL. The developmental trajectory of log testosterone was like that of log LH, but rose less steeply early in puberty. From 0.14 micrograms/L at a testis volume of 1 mL, testosterone increased about 8.5-fold by 10 mL and an additional 3-fold by 30 mL. In contrast, logarithms of overnight mean FSH and alpha-inhibin concentrations rose at a more nearly constant rate throughout puberty. From 0.62 IU/L at a testis volume of 1 mL, the FSH concentration doubled by 10 mL and increased an additional 1.7-fold by 30 mL. From 270 ng/L at a testis volume of 1 mL, inhibin increased 1.5-fold by 10 mL and an additional 1.3-fold by 30 mL. Overnight pulse amplitudes exhibited developmental trajectories similar to those of the corresponding overnight mean concentrations. The number of LH and testosterone pulses during the sampling period averaged 2.2 and 2.1, respectively, at Tanner stage 1 and increased to 4.5 and 3.2, respectively, at Tanner stage 5. The number of FSH and inhibin pulses remained constant throughout puberty, averaging 3.3 and 3.5, respectively. Pairwise correlations among hormone concentrations were strong, reflecting common increasing trends through puberty; however, after accounting for developmental trends, FSH, LH, and testosterone concentrations remained correlated, whereas inhibin was uncorrelated with each of the other three hormones. Measuring gonadotropins with ultrasensitive assays and analyzing the results on a logarithmic scale as a function of testis volume made clear the dramatic hormonal changes that begin before the clinical changes of puberty.     

Mid-follicular phase pulses of inhibin B are absent in polycystic ovarian syndrome and are initiated by successful laparoscopic ovarian diathermy: a possible mechanism regulating emergence of the dominant follicle

The hypothalamic pulse generator of GnRH is recognized to be central to ovulatory function as evidenced by the anovulation of women with hypogonadotrophic hypogonadism due to Kallmann's syndrome or severe anorexia nervosa. LH is released from the anterior pituitary in pulses, the frequency of which is closely entrained with those of GnRH. In contrast, secretion of FSH is influenced by a number of regulatory molecules, including GnRH, estradiol, inhibin, and activin. The close temporal relationship between changes in levels of inhibin B and FSH in the mid-follicular phase suggests that the release of inhibin B by the preovulatory follicle critically regulates pituitary FSH secretion. Polycystic ovarian syndrome (PCOS) is one of the most common endocrine disorders affecting ovulation, and abnormal ovarian morphology as detected by ultrasonography remains the most sensitive diagnostic marker for this disorder. The etiology of PCOS is unclear, but its effective treatment by both anti-estrogens and by exogenous FSH suggests that a primary disorder of FSH regulation may be central. To investigate the possible role of inhibin B in the pathology of PCOS, serum inhibin B levels were measured in 10 women with PCOS on cycle day 5 of a spontaneous or progestrogen-provoked bleed and compared with levels on cycle day 5 of 10 women with regular ovulatory cycles. The mean serum inhibin B levels in the PCOS patients were significantly higher at 248 (+/- 43.4) pg/mL compared with normal controls, 126 (+/- 18.6) pg/mL (P < 0.01). Ten women with clomiphene resistant PCOS and 5 normal controls consented to undergo serial blood sampling on cycle day 5. Time Series Analysis using a Fourier Transformation to analyze the power spectrum of the data revealed that in normal women there is a distinct periodicity in inhibin B levels with a clear peak detectable every 60-70 min (P < 0.05), whereas in women with ovulatory dysfunction due to PCOS, no such pattern of regular pulsatility was seen. Four women with PCOS whose anovulation was successfully treated with laparoscopic ovarian diathermy (LOD) underwent repeat venous sampling following LOD. Their serum inhibin B levels fell to the upper limit of the normal range (160 +/- 38.5) pg/mL, and pulsatility was initiated. It is possible that inhibin B pulses are being generated directly by the ovary in response to pulses of GnRH in the peripheral circulation, or indirectly in response to FSH pulses arising in the pituitary. The function of inhibin B pulses in the mid-follicular phase of the normal cycle remains to be elucidated, but the absence of the normal pulsatile pattern in women with PCOS, in conjunction with high basal levels of inhibin B arising from the multiple small follicles characteristic of the PCOS ovary, appears to reinforce the development of a large cohort of small, developmentally arrested, and ultimately atretic follicles in these patients. Initiation of normal inhibin B pulsatility by LOD in patients with polycystic ovaries appears to correlate with the post-operative onset of ovular cycles.     

Changes in gene expression following traumatic brain injury in the rat

1. The relationship between immunoreactive inhibin and follicle-stimulating hormone (FSH) was studied in male and female chickens from hatch to sexual maturity. Plasma inhibin was estimated by a heterologous radioimmunoassay validated for use in the chicken. FSH was measured by a recently developed homologous radioimmunoassay. 2. In a cross-sectional study, blood samples and gonads were collected from chickens of both sexes at 1, 3, 5, 7, 14, 21 and 28 d after hatching and subsequently at 14-day intervals until 182 d of age. 3. In the female, plasma progesterone concentration (P4) progressively increased during sexual development. The plasma luteinising hormone (LH) concentration rose during the first week after hatching, and fluctuated thereafter, with troughs at 6 and 14 weeks and peaks at weeks 10 and 18. The plasma inhibin and FSH concentrations remained low until the start of puberty and increased simultaneously thereafter. However, from week 18 on, plasma inhibin continued to rise while plasma FSH fell. Hence, FSH and inhibin were positively correlated before puberty, but developed a negative correlation during sexual maturation. 4. In the male, plasma testosterone and LH concentrations increased 38- and 3.7-fold respectively over the period studied. Inhibin and FSH followed similar time courses and were consequently positively correlated. 5. These results suggest sex differences in the role of inhibin in regulating FSH secretion during development. The FSH-inhibin feedback loop may become operational at the onset of sexual maturity in the hens. In male chickens, the similar pattern of inhibin and FSH secretion suggests that inhibin secretion is driven by FSH.     

Gonadotropins are essential modifier factors for gonadal tumor development in inhibin-deficient mice

We previously demonstrated that mice deficient in inhibin develop gonadal sex cord-stromal tumors with nearly 100% penetrance. These ovarian and testicular tumors develop as early as 4 weeks of age and eventually cause cachexia-like symptoms and death in the inhibin-deficient mice. Gonadectomized inhibin-deficient mice initially do not develop this wasting syndrome, but eventually will develop adrenal cortical tumors with similar penetrance. These studies have demonstrated that inhibin is a secreted type of tumor suppressor in the gonads and adrenal glands. Gonadotropins are implicated to influence gonadal tumor development in humans as well as experimental animals, and in inhibin-deficient mice, serum FSH levels are elevated. To determine whether gonadotropins influence the development and/or progression of the tumors in the inhibin-deficient mice, we took advantage of a naturally occurring mutant mouse, hypogonadal (hpg); hpg/hpg mice lack a functional GnRH gene and, therefore, have suppressed FSH and LH levels. Heterozygous hpg/+mice were crossed to heterozygous inhibin mutant mice to generate compound homozygous mutant mice that lack both inhibin and GnRH. These compound homozygous mutant mice do not develop a wasting syndrome, do not exhibit gonadal or adrenal tumors, and can survive for more than 1 yr. These results demonstrate that gonadotropins are essential modifier factors for tumor development in inhibin-deficient mice.     

Recombinant human inhibin-A administered early in the menstrual cycle alters concurrent pituitary and follicular, plus subsequent luteal, function in rhesus monkeys

Inhibin, a suppressor of pituitary FSH secretion in nonprimate species, may also act in the ovary to regulate follicular development. To examine whether inhibin has similar actions in primates, female rhesus monkeys (n = 3/treatment), exhibiting regular menstrual cycles, received sc injections of either vehicle or 60 micrograms/kg recombinant human inhibin-A at 0800 and 1600 h for 5 days beginning at menses. The vehicle-treated monkeys displayed menstrual cycles of normal length, with the follicular (11.3 +/- 2.5 days, mean +/- SE) and luteal (16.3 +/- 2.5 days) phases demarcated by midcycle peaks in serum estradiol (E) and bioactive LH. After the first inhibin injection, levels of immunoreactive inhibin A peaked at 10 ng/mL within 1 h and returned to baseline (< 0.1 ng/mL) before the second injection 8 h later. Although serum E and LH did not change, bioactive FSH decreased (to 66% of pretreatment levels, P < 0.05) within 8 h. Within 1 day, circulating bioactive FSH was less (P < 0.05) in inhibin-treated monkeys, compared with controls. By 2-3 days, serum E levels were also markedly (P < 0.05) reduced in inhibin-treated animals, whereas bioactive LH rose 3-fold (P < 0.05). After inhibin treatment, the midcycle rises in serum E and LH were delayed; hence, the follicular phase was prolonged (15.0 +/- 2.6 days, P < 0.05), compared with controls. Although the patterns and levels of serum LH circulating during the subsequent luteal phase seemed comparable in both groups, mean progesterone levels were suppressed to 2-3 ng/mL (P < 0.05) during the midluteal phase in inhibin-treated monkeys. However, the length of the luteal phase in inhibin-treated cycles (13.0 +/- 2.6 days) was not significantly altered. We conclude that exogenous inhibin rapidly diminishes pituitary FSH secretion in female monkeys during the early follicular phase of the menstrual cycle. This action, and/or other actions directly on the ovary, leads to subsequent effects on follicular steroidogenesis and pituitary LH secretion that culminate in an aberrant ovarian cycle characterized by an insufficient luteal phase. The study identifies, for the first time, possible activities and roles of inhibin during the ovarian cycle in primates.     

Inhibin B is the major form of inhibin/activin family secreted by granulosa cell tumors

Both experimental and clinical studies suggest that inhibin plays a critical role in the development of granulosa cell tumors (GCT), a subgroup of malignant ovarian tumors. Inhibin has been proposed as a biological marker for the follow-up of patients bearing these particular tumors. Hitherto, there is no general agreement on the molecular form(s) of the inhibin family that are secreted by malignant granulosa cells. Using specific and sensitive immunoassays for activin A and for inhibins A and B, we investigated the production of these molecules in patients with either an adult GCT (n=13) or an epithelial ovarian cancer (n=11). Results showed that serum activin A level was increased in all patients, independently of their clinical status (progressive disease or remission) in comparison to that observed in the healthy pre- and postmenopausal women. Most of the patients also presented a moderate increase in serum inhibin A level compared to that in controls. Only one of eight patients with a progressive granulosa cell tumor had a high value of serum inhibin A. In contrast, serum inhibin B was dramatically increased in eight of nine patients with a granulosa cell tumor and its level correlated with the clinical status of the patients. No correlation was found between the level of serum inhibin B and that of serum antimüllerian hormone, a recently described specific and reliable marker for GCT. None of the patients with an epithelial ovarian cancer presented an increase of serum inhibin B. These observations demonstrate that inhibin B is the major molecular form of the inhibin family proteins produced by malignant granulosa cells.     

Serum leptin levels in normal children: relationship to age, gender, body mass index, pituitary-gonadal hormones, and pubertal stage

It is commonly accepted that at least in girls puberty starts when a minimum level of body mass or a certain amount of body fat are present. However the precise signal by which adipose stores inform the hypothalamus of the degree of energetic reserves is unknown. Leptin is a hormone produced by the adipocytes to regulate food intake and energy expenditure at the hypothalamic level. To understand whether leptin is the adipose tissue signal that allows puberty, 789 normal children of both sexes, age 5-15 yr, were transversally studied. Leptin levels, as well as gonadal and gonadotropins, levels, were analyzed in addition to the determination of auxological parameters. In an age-related analysis, leptin levels in girls rose from 5-15 yr (from 4.3 +/- 0.4 to 8.5 +/- 0.9 micrograms/L) in parallel with body weight. Boys always had lower leptin levels than girls (3.3 +/- 0.3 micrograms/L at 5 yr), but they rose in parallel with weight until 10 yr (5.3 +/- 0.7 micrograms/L), when a striking decrease was observed until 15 yr (3.0 +/- 0.3 micrograms/L). In girls, leptin was the first hormone to rise followed by FSH and later by LH and estradiol. A similar pattern occurred in boys, despite the fact that leptin dropped after 10 yr when testosterone rises. Divided into three pubertal stages, i.e. P1 = prepuberty, P2 = early puberty, and P3 = overt puberty, in girls the four hormones rose progressively from P1 to P3, but from P2 to P3 the present increment was greater for LH and estradiol. In boys, leptin decreased from P1 to P3, whereas FSH, LH, and testosterone rose. The age-related changes were not caused by adiposity variations, because data did not change when subtracting values of children over 97% of standard deviation score of body mass index. In conclusion: 1) leptin appears to increase in both boys and girls before the appearance of other reproductive hormones related to puberty; 2) leptin levels in boys are always lower than in girls, although they increase with age until the age 10 yr; 3) leptin in boys declines about the time testosterone increases. Leptin may well be a permissive factor for the initiation of pubertal events.     

Inhibin A, inhibin B and activin A in the follicular fluid of regularly cycling women

Recent measurements of circulating inhibin A and inhibin B concentrations indicate that inhibin B may play an important role in the selection of dominant follicles. The concentrations of inhibin A, inhibin B and activin A were measured in the follicular fluids of 61 individual follicles (4.8-20 mm in diameter) from 47 regularly cycling women using specific two-site enzyme-linked immunosorbent assays. The microenvironment of each follicle was characterized by measuring follicular fluid androstenedione and oestradiol concentrations. The mean activin A concentrations were < 8 ng/ml for follicles of all sizes (4-17 mm). Inhibin A concentrations were < 1 ng/ml in follicles < 6 mm, and progressively increased to concentrations > 50 ng/ml in follicles > or = 13 mm. Follicles with androstenedione/oestradiol ratios < or = 4 had higher concentrations of inhibin A than follicles with androstenedione/oestradiol ratios > 4. Inhibin B concentrations were higher than inhibin A concentrations in all follicles, increasing from 19.2 +/- 8.3 ng/ml in 4 mm follicles to 409 +/- 9.6 ng/ml in 13 mm follicles and then declining to 275 +/- 47 ng/ml in 17 mm follicles. These results support the hypothesis that inhibin B may play a more important paracrine role in developing follicles and a greater regulatory role with respect to follicle stimulating hormone (FSH) secretion than inhibin A.     

Charge interactions in sperm-egg recognition

The effect of androgens on changes in circulating LH and FSH during pubertal development was examined longitudinally in a 3 year study in male hamadryas baboons. Baboon LH and FSH were measured by a species-specific radioimmunoassay and bioactive LH (B-LH) was measured by the mouse in vitro Leydig cell bioassay. Control baboons (n = 5) progressed normally through puberty. Eight baboons were castrated prepubertally; of these four received testosterone implants at the chronological age (CA) of clinical puberty (4.0 +/- 0.1 yr, mean +/- SEM). The timing of the postcastration rise in B-LH levels ranged between 1 and 15 months later (median 3.5 months) (CA 3.5 +/- 0.2 yr) thus supporting the hypothesis that central activation of gonadotrophins occurs at the time of puberty, independent of gonadal influences. Similar results were seen for immunoreactive-LH (IR-LH) and IR-FSH levels. IR- and B-LH levels continued to rise with age (P < 0.0003) in the untreated castrated baboons, associated with an increased LH B/I ratio. Administration of testosterone resulted in temporary suppression of B-LH, IR-LH and IR-FSH levels; however gonadotrophin levels subsequently rose with age despite increased testosterone levels. Thus the mechanisms initiating puberty involve both gonad-independent events as well as alterations in negative androgenic feedback sensitivity on gonadotrophin secretion.     

Suppression of spermatogenesis in man induced by Nal-Glu gonadotropin releasing hormone antagonist and testosterone enanthate (TE) is maintained by TE alone

GnRH antagonists plus testosterone (T) suppress LH and FSH levels and inhibit spermatogenesis to azoospermia or severe oligozoospermia. High-dose T treatment alone has been shown to be an effective male contraceptive (contraceptive efficacy rate of 1.4 per 100 person yr). Combined GnRH antagonist and T induces azoospermia more rapidly and at a higher incidence than T alone; this combination has therefore been proposed as a prototype male contraceptive. However, because GnRH antagonists are expensive to synthesize and difficult to deliver, it would be desirable to rapidly suppress sperm counts to low levels with GnRH antagonist plus T and maintain azoospermia or severe oligozoospermia with T alone. In this study, 15 healthy men (age 21-41 yr) with normal semen analyses were treated with T enanthate (TE) 100 mg im/week plus 10 mg Nal-Glu GnRH antagonist sc daily for 12 weeks to induce azoospermia or severe oligozoospermia. At 12-16 weeks, 10 of 15 subjects had zero sperm counts, and 14 of 15 had sperm counts less than 3 x 10(6)/mL. The 14 who were suppressed on combined treatment were maintained on TE alone (100 mg/week im) for an additional 20 weeks. Thirteen of 14 subjects in the TE alone phase had sperm counts maintained at less than 3 x 10(6)/mL for 20 weeks. Ten remained persistently azoospermic or had sperm concentration of 0.1 x 10(6)/mL once during maintenance. Mean LH and FSH levels in the subjects were suppressed to 0.4+/-0.2 IU/L and 0.5+/-0.2 IU/L in the induction phase, which was maintained in the maintenance phase. The 1 subject who failed to suppress sperm counts during induction had serum LH and FSH reduced to 0.3 and 0.5 IU/L, respectively. The subject who failed to maintenance had LH and FSH suppressed to 1.0 and 0.2 IU/L, respectively, during the induction phase but these rose to 1.6 and 2.1 IU/L, respectively, during maintenance. Failure to suppress or maintain low sperm counts may be related to incomplete suppression of serum LH and FSH levels. We conclude that sperm counts suppressed with GnRH antagonist plus T can be maintained with relatively low dose TE treatment alone. This concept should be explored further in the development of effective, safe, and affordable hormonal male contraceptives.     

Activin A and inhibin B in extra-embryonic coelomic and amniotic fluids, and maternal serum in early pregnancy

Activin A and inhibin B levels were measured, using a two-site enzyme immunoassay, in extra-embryonic coelomic fluid, amniotic fluid and maternal serum samples retrieved from 23 healthy pregnant women, at 8 (n=8), 9 (n=8), and 10 (n=7) weeks of gestation. Dimeric activin A and inhibin B were measurable in all samples. Median (+/-SEM) activin A concentrations in coelomic fluid (0.98+/-0.34 ng/ml) were significantly higher than in maternal serum (0.68+/-0.05 ng/ml) and in amniotic fluid (0.09+/-0.04 ng/ml) (P<0.05). Maternal serum activin A levels were significantly higher than amniotic fluid concentrations. Median (+/-SEM) inhibin B concentrations in coelomic fluid (24.32+/-6.02 pg/ml) were significantly higher than in maternal serum (5.94+/-0.97 pg/ml) and in amniotic fluid (6.31+/-1.53 pg/ml) (P<0.05), while no significant difference between maternal serum levels and amniotic fluid concentrations was found. No significant difference in activin A and inhibin B levels in extra-coelomic fluid, amniotic fluid, and maternal serum throughout the 3 weeks of pregnancy was found. The present study showed that coelomic fluid is an important reservoir of activin A and inhibin B, supporting the hypothesis that the extra-embryonic coelom may have a secretory role during the first 11 weeks of gestation.     

Elevated ovarian expression and serum concentration of alpha inhibin in the luteal phase during follicular development in the squirrel monkey (Saimiri boliviensis) compared to the human

The goal of the present investigation was to determine in the squirrel monkey the source and pattern of inhibin, a hormone known to effect reproductive steroid levels via pituitary and ovarian mechanisms. Since this seasonally polyestrous species is known to have elevated serum levels of reproductive steroids compared to other primates, the levels of ovarian alpha subunit mRNA expression and serum total alpha inhibin, estradiol, progesterone, and luteinizing hormone were measured and compared to human levels. Expression of the alpha subunit was robust in monkey luteal tissue compared to expression in human luteal tissue. Squirrel monkey serum inhibin peaked 4 days after the luteinizing hormone surge and correlated with progesterone changes. These luteal serum levels of inhibin were greater than 12 times higher than the human levels yet bio-LH activities were less than in the human during the luteal phase. Inhibin concentrations during the nonbreeding season were generally half the levels measured in the breeding season and undetectable in ovariectomized animals. However, exogenous FSH stimulation induced a marked rise in inhibin, which correlated with an estradiol rise. In conclusion, abundant alpha inhibin subunit expression in the luteal ovary of the squirrel monkey and loss of serum delectability in ovariectomized animals indicates that the principle source of inhibin in the squirrel monkey is the ovary. Elevated serum inhibin levels during the luteal phase concurrent with ovulatory-size follicular development is unique among species studied thus far. Possible simultaneous inhibin production from both follicular and luteal tissue may be responsible for the exceptionally high inhibin levels.