Basal inhibin B and the testosterone response to human chorionic gonadotropin correlate in prepubertal boys

During childhood, the quiescent phase of testicular activity, the hCG stimulation test is widely used to evaluate testicular function. Inhibin B, a gonadal peptide regulating FSH secretion, is an established marker of Sertoli cell function and spermatogenesis in adults. In contrast to the other hormones of the hypothalamo-pituitary-gonadal axis, inhibin B is also secreted in detectable amounts during childhood. The aim of this study was to determine whether basal inhibin B levels are able to predict prepubertal testicular function, so as to avoid a stimulation test. Inhibin B and testosterone before and after hCG stimulation were measured in 54 male children with various testicular disorders by an immunoassay specific for inhibin B. Basal inhibin B was compared to the testosterone increase after hCG. Inhibin B and the hCG-induced testosterone increment correlated strongly (r = 0.84; P<0.0001). Patients with anorchia were clearly distinguishable from those with abdominal testes, having undetectable (inhibin B, <15 pg/mL) respective normal inhibin B levels for age. Inhibin B and the testosterone response to hCG were low in boys with testicular damage (delayed diagnosis of cryptorchidism; after testicular torsion) and in patients with gonadal dysgenesis, but were normal or increased in children with androgen insensitivity syndrome. We conclude that basal inhibin B predicts the testosterone response to hCG in boys and therefore gives reliable information about both the presence and function of the testes. The diagnostic procedure in cryptorchidism may be reduced to a single inhibin B measurement. Furthermore, inhibin B levels show specific alterations in patients with sexual ambiguity, adding a valuable diagnostic tool to the complex differential diagnosis of male pseudohermaphroditism.     

Pituitary gonadotropin function during human pregnancy: serum FSH and LH levels before and after LHRH administration.

Pituitary gonadotropin reserve was evaluated in 8 normal pregnant women (13-35 weeks gestation) by measuring serum concentrations of FSH and LH (betaLH assay) before and after an IV bolus of 100 mug LHRH. Basal levels of FSH and LH were low or undetectable. LHRH administration failed to stimulate FSH release but did result in a small short-lived rise in LH levels. These findings provide further evidence that pituitary gonadotropin synthesis and release are inhibited during pregnancy.     

Plasma LH and FSH response to LRH and plasma testosterone levels in boys with irregular puberty.

Nineteen boys with irregular puberty (IP), defined as a discrepancy of two or more pubertal stages between the criteria for genitalia and that for pubic hair, were subjected to a standard LRH test (50 microng/m2, iv) and the response of gonadotrophins as well as the basal levels of plasma testosterone, LH and FSH were compared to those of boys with normal, regular puberty. When the results were plotted against the pubertal stage for genitalia (Pg), it was found that in the boys with IP the basal plasma testosterone levels were lower and the response of plasma LH to LRH stimulation lesser than in the controls. However, when these parameters were plotted against the pubertal stage for pubic hair (Ph) it was found, that in the boys with IP the plasma testosterone levels were significantly higher and the response of both LH and FSH stimulation greater than in the control group. It was concluded that irregular puberty in boys may be regarded as a normal variation. The delayed development of sexual hair and penile length, and retarded pubertal growth spurt and bone age maturation seen in these boys, with normal testicular development, may be explained by a temporary reduced peripheral sensitivity to androgens and a compensatory effort by the pituitary, manifested in increased secretion of LH and testosterone, relatively to their pubertal stage for pubic hair.     

Inverse correlation between baseline inhibin B and FSH after stimulation with GnRH: a study of serum levels of inhibin A and B, pro alpha-C and activin A in women with ovulatory disturbances before and after stimulation with GnRH

OBJECTIVE: Interest has focused recently on the influences of the polypeptide factors inhibin and activin on the selective regulation of the pituitary secretion of gonadotropins. DESIGN: Measurement of the concentrations of inhibin-related proteins in relation to the changes in pituitary gonadotropin (FSH, LH) parameters, after GnRH stimulation with a bolus injection of 100 microg gonadorelin, in 19 women with ovulatory disturbances. METHODS: Serum levels of inhibin A and B, activin A, and pro alpha-C were measured using sensitive ELISA kits. RESULTS: Within 60 min after GnRH stimulation, FSH values doubled from 5 to 10 mU/ml (P < 0.001). LH increased 12-fold from 2 to 24 mU/ml (P < 0.001). Activin A showed a significant decrease from 0.47 to 0.36 ng/ml (P < 0.001), whereas pro alpha-C increased from 127 to 156 pg/ml (P = 0.039). The median inhibin A concentration did not show a significant change between baseline and the 60 min value, whereas inhibin B was characterized by a minor, but not significant, increase in the median from 168 to 179 pg/ml (P = 0.408). A significant inverse correlation (P = 0.014) with a mean coefficient of correlation of 0.5516 was found, demonstrating a strong relationship between high inhibin B baseline levels and a small increase of FSH after 60 min. CONCLUSION: Our results show an interesting correlation between the baseline inhibin B and the change in FSH before and after GnRH stimulation. A high baseline inhibin B implies only a minor increase of FSH after 60 min.     

Plasma androgen responce to hCG stimulation in prepubertal boys with hypospadias and cryptorchidism.

Serum levels of testosterone, androstenedione and dehydroepiandrosterone were measured before and after 5 days of treatment with hCG (2000 IU/d) in 36 prepubertal boys with cryptorchidism and 11 with hypospadias in order to determine whether a defect in androgen synthesis could be a common cause for these disorders. Baseline and stimulated levels of testosterone, androstenedione and dehydroepiandrosterone were similar in patients with unilateral cryptorchidism, monorchism and hypospadias; baseline and stimulated levels of testosterone were lower in boys with bilateral cryptorchidism. Testosterone levels did not correlate with either the anatomical location of the testis in patients with unilateral cryptorchidism or with the site of the urethra in boys with hypospadias. Seven of 36 patients with cryptorchidism had a positive family history of a similar disorder; testosterone levels were similar in patients with and without a family history. It is concluded: 1) in all patients studied, the gonadotropin dependent phase of testosterone production is present; 2) hCG stimulation cannot detect unilateral Leydig cell dysfunction; and 3) in familial cases of cryptorchidism, some factor other than an abnormality in androgen synthesis may be responsible for the hereditary tendency.     

健康婴儿LH、FSH、雌二醇与睾酮的血清浓度

目的研究正常婴儿血LH、FSH、雌二醇(E2)与睾酮(T)的血清浓度变化。方法用免疫化学发光分析法对358名正常婴儿(男婴183,女婴175)的LH、FSH、E2和T水平进行测定,同时对3个月内婴儿的其他可能相关指标(出生体重、孕期、胎次、母亲年龄及分娩方式)进行了研究。结果(1)婴儿期4种激素水平变化男婴LH、FSH在2~3月龄时达高峰(LH3.5IU/L,FSH3.4IU/L),6月龄后趋平坦(LH1.5IU/L,FSH<1.5IU/L),T在2~4月龄时达高峰(9.15mmol/L)后快速下降,6月龄后稳定在一个较低的水平(<1.34nmol/L);女婴FSH在2~3月龄达高峰(7.1IU/L),LH与T在整个婴儿期的水平几乎是条直线(LH<4.7IU/L,T<2.49nmol/L)。男女婴的E2水平在生后快速下降,3月龄后达最低值。(2)性别差异LH和T在6月龄前男婴明显高于女婴,6月龄后无性别差异。FSH水平各月龄组女婴均高于男婴,E2除2月龄前女婴高于男婴外,3~12月龄时无性别差异。(3)3月龄内婴儿促性腺激素、性激素水平与出生体重、孕期、胎次、母亲年龄及分娩方式未显示相关关系。结论婴儿在2~4月龄时的血促性腺激素与性激素水平有个暂时的高峰期,并有明显性别差异,可能与两性性腺发育的不同调控机制有关。     

Testicular blood flow, vascular permeability, and testosterone production after stimulation of unilaterally cryptorchid adult rats with human chorionic gonadotropin

Testicular blood flow, testosterone production, and the formation of testicular interstitial fluid (IF) were studied in unilaterally cryptorchid rats, basally, 8 h and 24 h after treatment with 200 IU human CG (hCG). Testicular blood flow was lower in the abdominal testis in both control rats and hCG-treated rats than in the scrotal testis within the same treatment group. The scrotal testicular blood flow increased significantly 24 h after hCG treatment, but not after 8 h. In the abdominal testis, there was a significant increase of blood flow 8 h after hCG, but not 24 h after. The formation of IF was subnormal in the abdominal testes of control rats, but this was corrected in hCG-treated rats, where there was a significant increase of IF in both abdominal and scrotal testes. The total endothelial surface of small blood vessels was decreased in abdominal testes. Testosterone concentration in the spermatic vein was significantly lower on the abdominal side than on the scrotal side in both control and hCG-treated rats. The concentration of testosterone was lower in IF on the abdominal side in control rats, but after hCG the testosterone concentration was similar in both scrotal and abdominal testes, indicating a trapping of testosterone in the abdominal testis. The outflow of testosterone in the spermatic vein was significantly increased at both 8 and 24 h after hCG from both the scrotal and abdominal testes, although it was always smaller from the abdominal testis. The lower secretion of testosterone from the abdominal testis after hCG was mainly due to reduced blood flow and not to any disability of the Leydig cells of abdominal testes to produce testosterone.     

Sex hormone-binding globulin response to human chorionic gonadotropin stimulation in children with cryptorchidism, anorchia, male pseudohermaphroditism, and micropenis

Sex hormone-binding globulin serum concentrations (SHBG) were measured before and after a 5-day hCG stimulation test in 11 prepubertal boys with cryptorchidism, 6 with anorchia, 5 with male pseudohermaphroditism, and 5 with micropenis. Cryptorchid boys had decreased SHBG levels after hCG, by 55 +/- 17% (mean +/- SE) of the basal concentration. Patients with anorchia, who did not show an elevation in serum androgens, did not have decreased SHBG concentrations. Four of the 5 patients with male pseudohermaphroditism had an adequate elevation of serum androgens, did not have decreased SHBG concentrations. Four of the 5 patients with male pseudohermaphroditism had an adequate elevation of serum androgens after hCG, but in only 3 of them did SHBG decrease. None of the 5 patients with micropenis had decreased serum SHBG levels despite normal increments in serum androgens. The administration of a long-acting preparation of testosterone to sexually infantile subjects produce a similar decrease in the SHBG concentration. This change in SHBG concentration after hCG or testosterone in prepubertal boys could be used as a convenient test of biological response to androgens.     

Pubertal sleep-wake patterns of episodic LH, FSH and testosterone release in twin boys.

On 2 consecutive nights, plasma LH, FSH and testosterone (T) were measured every20 min for 12 h during evening wakefulness and polygraphic sleep in 5 pairs of male monozygotic twins in pubertal stages 1-4, and in a male dizygotic also studied in 3 twins. During sleep, significant enhancement of episodic LH release was seen on 16 of 18 nights on the stage 1-4 twins. During wakefulness, minimal episodic LH release was observed in the stage 1-3 twins, which then gradually increased in the more mature twins, until finally the significant sleep-wake difference in mean LH was lost in the stage 5 male. Testosterone also rose significantly in sleep on 19 of 20 study nights in the stage 1-5 twins. In the early pubertal twins this nocturnal rise in T was small, but in the midpubertal pairs it was profound, as peaks in T occurred which lay in the normal range for adult males. In these less mature twins the majority of the episodic secretion of T also was limited to sleep. In wakefulness, the T levels gradually increased across puberty until, in the stage 5 twin, wakeful peaks in T finally reached the adult male range. In the midpubertal twins, a close temporal relationship was seen between initiation of sleep-enhanced LH release and the subsequent initial rise in T (mean lag time 29.1 min). In the stage 5 twin, this episodic LH-T relationship persisted into wakefulness where the largest increments in T were seen just prior to sleep onset. Evidence of sleep-enhanced FSH release was more equivocal, and was limited mainly to pubertal stage 1 and 3 pairs. Similarities in hormonal patterns were seen within the monozygotic twin pairs and probably contributed to the parallel progress in puberty of the pair. Thus, sleep-wake rhythmicity in release of gonadotropins, particularly LH and thereby of testosterone, was seen to evolve transiently in twin boys across puberty. The existence of such rhythmicity suggests that a fundamental, sleep-entrained CNS mechanism plays an important, if not a dominant, role in sexual maturation in boys.     

Production of inhibin bioactivity by human granulosa-lutein cells: stimulation by LH and testosterone in vitro

Granulosa-lutein cells from human preovulatory ovarian follicles were cultured for up to 12 days to determine their capacity for production of inhibin in vitro. Using a highly sensitive sheep pituitary cell bioassay we observed time-related changes in basal inhibin production, maximal during the first 4 days of culture (48 +/- 15 units/million cells every 2 days, means +/- S.E.M.; n = 5 patients) falling to values five times lower by day 12. After 4-6 days of culture in the presence of human LH (hLH) inhibin production was enhanced in proportion to the hLH dose (maximum five fold at 10 ng/ml); hFSH over the same dose-range had no effect. Progesterone production in response to hLH followed a similar pattern to that of inhibin and was also unresponsive to hFSH. In the absence of exogenous aromatase substrate, basal and gonadotrophin-stimulated oestradiol production was negligible after the first 4 days. Addition of testosterone (1 mumol/l) to the culture medium increased oestrogen formation several hundred-fold with no effect on progesterone production. Inhibin production was also increased by 50-100% in the presence of testosterone. These results demonstrate that LH and testosterone stimulate the production of inhibin by granulosa-lutein cells in vitro. It is suggested that inhibin production occurs under hormonal control in the corpus luteum as well as in the preovulatory follicle in the human ovary.     

IGF-I, IGF-BP3, and GH serum levels after stimulation tests in prepubertal allergic boys.

The prevalence of short stature (SS, < 3rd percentile NCHS) among children with respiratory allergy (asthma and/or rhinitis) varies from 2% to 10%. In spite of several studies, the etiology of SS in those patients remains unknown. We evaluated growth hormone (GH) serum levels in response to two stimulating tests (standardized exercise and clonidine) in prepubertal boys (G1P1, Tanner; 8 years and 5 months to 14 years) with SS, 14 of them with respiratory allergy (A, positive skin prick test to D. pteronyssinus) and 5 nonallergic children (NA). Other causes of SS were excluded in both groups. Patients had mild asthma and/or rhinitis, and they had never received inhaled or systemic corticosteroid at any time. Tests were performed on different days, at least 1 week apart. [To prevent exercise-induced asthma, 30 min before the exercise test, allergic children inhaled disodium cromoglycate (2 mg)]. GH serum levels (Immunoassay, AIA-PACK HGH, Tosoh Co, Japan) were determined at the following times: exercise (E)--basal, 5, 15, and 30 min after exercising for 6 min; clonidine (C)--basal, 30, 60, and 90 min after clonidine (0.15 mg/m2 body surface) ingestion. A response was considered positive when GH serum levels reached the minimum of 10 ng/ml. Among (the allergic) A patients, four responded to both tests, five to C (clonidine) alone, four to E (exercise) alone and one had no response. Among NA, four had a positive response to both tests and one to C (clonidine) alone. The serum levels of insulin-like growth factor I (IGF-I) (DSL-5600 Active TM IGF-I Coated-Tube IRMA [DSL Lab Inc, USA]) and its binding protein (IGF-BP3) (DSL-6600 Active TM IGF-BP3 Coated-Tube IRMA [DSL Lab Inc, USA]) were within the normal range except for one A child. Bone age was delayed in relation to chronological age in all children, but adequate for height age. All children had delayed skeletal age in relation to chronological age, but bone age was normal for height. We concluded that in the children studied a deficiency of GH does not seem to be responsible for SS.     

Short term growth in boys with delayed puberty after diagnostic human chorionic gonadotropin administration.

Using a sensitive measuring device, 3-day hCG administration (Pregnyl; 1500 IU daily) was shown to temporarily increase ulnar growth velocity from prepubertal (0.40 +/- 0.35 mm/3 weeks to pubertal values (1.1 +/- 0.64 mm/3 weeks) in 10 boys with delayed puberty. This growth-promoting effect of diagnostic hCG administration, which was demonstrable for 3--9 weeks, was associated with an overt rise in plasma testosterone from 129 +/- 126 to 818 +/- 419 ng/100 ml and an approximate doubling of the serum alkaline phosphatase activities from 193 +/- 46 to 376 +/- 115 U/liter, suggesting an initiated growth spurt.     

Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression

In previous studies of testicular biopsy tissue from healthy men, intratesticular testosterone (ITT) has been shown to be much higher than serum testosterone (T), suggesting that high ITT is needed relative to serum T for normal spermatogenesis in men. However, the quantitative relationship between ITT and spermatogenesis is not known. To begin to address this issue experimentally, we determined the dose-response relationship between human chorionic gonadotropin (hCG) and ITT to ascertain the minimum dose needed to maintain ITT in the normal range. Twenty-nine men with normal reproductive physiology were randomized to receive 200 mg T enanthate weekly in combination with either saline placebo or 125, 250, or 500 IU hCG every other day for 3 wk. ITT was assessed in testicular fluid obtained by percutaneous fine needle aspiration at baseline and at the end of treatment. Baseline serum T (14.1 nmol/liter) was 1.2% of ITT (1174 nmol/liter). LH and FSH were profoundly suppressed to 5% and 3% of baseline, respectively, and ITT was suppressed by 94% (1234 to 72 nmol/liter) in the T enanthate/placebo group. ITT increased linearly with increasing hCG dose (P < 0.001). Posttreatment ITT was 25% less than baseline in the 125 IU hCG group, 7% less than baseline in the 250 IU hCG group, and 26% greater than baseline in the 500 IU hCG group. These results demonstrate that relatively low dose hCG maintains ITT within the normal range in healthy men with gonadotropin suppression. Extensions of this study will allow determination of the ITT concentration threshold required to maintain spermatogenesis in man.     

Antiprogesterone RU486 increases serum immunoreactive inhibin levels and LH:FSH and testosterone:oestradiol ratios in cyclic rats.

Since administration of the antiprogesterone RU486 to cyclic rats results in a dissociation of basal LH and FSH secretion we studied its effects on peripheral levels of inhibin, oestradiol and testosterone throughout the oestrous cycle. Cyclic rats were given RU486 (2 mg) twice daily (09.00 and 17.00 h) on metoestrus, dioestrus and pro-oestrus. Oil-treated rats were used as controls. Serum concentrations of immunoreactive inhibin in oil-treated rats increased from metoestrus to pro-oestrus and decreased at oestrus. RU486-treated rats had serum inhibin concentrations significantly increased over oil-treated rats at dioestrus and pro-oestrus, but not at oestrus. At both pro-oestrus and oestrus serum concentrations of LH, testosterone and oestradiol were significantly raised in RU486-treated rats compared with oil-treated controls. In contrast, serum FSH concentrations in RU486-treated rats were decreased on both days. Ovaries from RU486-treated rats showed an increased testosterone content at pro-oestrus, mainly in the interstitial tissue. The results of the present study demonstrate that RU486 has a stimulatory effect on inhibin secretion, and offer an explanation for the decrease in basal serum FSH levels. The low FSH secretion on the morning of oestrus in spite of the low levels of inhibin suggests that progesterone is involved in FSH secretion at this time.     

Circadian variations in serum levels of LH, FSH, estradiol, testosterone and sex hormone binding globulin in acromegalic women with menstrual disturbances before and after transsphenoidal adenectomy

Day/night profiles of serum GH, PRL, IGF-I, LH, FSH, testosterone (TT and FT), estradiol (E2) and SHBG were estimated in 12 acromegalic women with GH- and PRL-producing pituitary adenomas and 13 patients with GH-secreting pituitary tumors before and 3 months after transsphenoidal adenectomy. All the subjects studied have had irregular menstrual cycles. Blood for profile determinations was drawn from a peripheral vein at 3 h intervals for three 24 h periods (starting at 08.00). Before surgery all acromegalic women had high mean 24 h GH and IGF-I levels (with irregular peaks) even in the absence of hyperprolactinemia. Postoperative mean 24 h GH level was still high only in 5 out of 25 women studied, and that of IGF-I in 10 of these patients. In 12 acromegalic women with preoperative hyperprolactinemia and disturbed 24 h fluctuations postoperative 24 h mean level of PRL and its circadian rhythm were normal. Before surgery, the circadian variations of pituitary-sex hormone levels and SHBG capacity in serum were not impaired. However, mean 24 h levels of LH, FSH, TT, FT E2 and SHBG were altered mainly in patients with mixed type of GH and PRL producing adenomas. This may be related to the increased activity of GH/IGF-I axis on the one hand and to the excess of PRL on the other. The postoperative normalization of pituitary-sex hormone levels and SHBG capacity in serum was noted only in women with normal 24 h circadian variations of IGF-I levels.     

Nocturnal secretory dynamics of inhibin B and testosterone in pre- and peripubertal boys

To investigate the secretory dynamics of testosterone and inhibin B, we collected samples every 20 min from 2000 h to 0800 h in 20 boys. Boys in group 1 (n = 5) were aged less than 8 yr, group 2 (n = 5) were aged more than 8 yr but 1.5 yr or more before pubertal onset, group 3 (n = 5) were studied 1.0 yr or less before pubertal onset, and group 4 (n = 5) were in early puberty. Testosterone increased after midnight in peripubertal boys, coinciding with the onset of LH pulsatility, and showed a pulsatile pattern in 6 of 10 of these boys. Cross-correlation analysis indicated significant temporal coupling between LH and testosterone. Inhibin B was higher in groups 3 and 4, compared with groups 1 and 2 (P < 0.01) and showed a downward trend overnight with no evidence of pulsatility and no evidence of short-term interactions with LH, FSH, or testosterone. Inhibin B and LH nocturnal means were both inversely correlated with time before pubertal onset (r(s) > or = -0.85, P < 0.01). Only LH nocturnal mean and amplitude, respectively, contributed independently to prediction of testosterone and inhibin B nocturnal means, explaining 71 and 65% of their variability. We conclude that both testosterone and inhibin B are related to nocturnal LH release in peripubertal boys but over different time scales.