An unexpected effect of oestradiol-17beta on luteinizing hormone and testosterone

Immunohistochemical localization of PGF2 alpha receptor in the mouse testis

As a step towards understanding the role of prostaglandin F2 alpha (PGF2 alpha) in male reproductive tract physiology, a rabbit polyclonal antiserum reactive with purified PGF2 alpha receptor (PGF2 alpha-R) was produced. Here we describe the use of this anti-PGF2 alpha-R antiserum in immunohistochemical staining of mouse testis to ascertain which cell types, in vivo, possess immunoreactive PGF2 alpha-R. As an initial control Western blot analysis was performed to show that the anti-PGF2 alpha-R antiserum recognizes only one antigen in the testis, and that this molecule is similar in molecular mass (by PAGE) to the previously described, purified PGF2 alpha-R molecule. Immunohistochemical staining demonstrates that adult mouse testis contains a single subpopulation of cells with PGF2 alpha-R and that subpopulation is the interstitial or Leydig cell subpopulation. Cell and tissue types negative for immunoreactive PGF2 alpha-R include: the capsule (tunica albuginea) and subcapsular stroma, all histologic layers of the vasculature (both venules and arterioles), peritubular stroma, peritubular boundary tissue, spermatogonia, primary and secondary spermatocytes, spermatids, Sertoli cells, and spermatozoa. While the above described localization of PGF2 alpha-R is also seen in rat, there are fewer rat Leydig cells and this subpopulation appears to atrophy and stain less intensely with increasing age of the animal. Preabsorption of the PGF2 alpha-R antiserum with a corpora lutea homogenate acetone powder eliminated immunohistochemical staining of the Leydig cell subpopulation further suggesting that the antigenic determinant detected here is related to that in the ovary (PGF2 alpha-R).

Treatment of men with idiopathic oligozoospermic infertility using the aromatase inhibitor, testolactone. Results of a double-blinded, randomized, placebo-controlled trial with crossover

The hypothesis that increased estradiol production may be the cause of impaired spermatogenesis in infertile men with idiopathic oligozoospermia was tested by administering the aromatase inhibitor, testolactone, and by assessing its effects on sperm output and fertility. Our study was a randomized, placebo-controlled double-blind crossover trial. Subjects (n = 25) with infertility due to unexplained oligozoospermia were given testolactone (2 g/day) or placebo for 8 months followed by crossover to the other treatment for an additional 8 months. Total estradiol and testosterone levels during testolactone exposure did not change from basal and placebo values. However, sex hormone-binding globulin binding capacity consistently decreased (30%, p less than 0.01) and free testosterone levels increased (36%, p less than 0.01). Free estradiol values increased but not significantly. Additionally, LH and FSH serum levels increased by 15% and 20%, respectively (p less than 0.05), and 17 alpha-hydroxyprogesterone values increased by 90% (p less than 0.05) during drug administration. Sperm output and semen quality remained unchanged during either testolactone or placebo treatment, and no pregnancies occurred during the 16-month study. These data suggest that chronic administration of testolactone at this dose fails to maintain aromatase inhibition despite depression of 17,20-desmolase activity with elevated 17 alpha-hydroxyprogesterone and depressed SHBG binding capacity with elevation of free testosterone. Testolactone is not efficacious in the treatment of idiopathic oligozoospermic infertility.

Lack of protection by oestrogen from radiation-induced testicular damage in the rat

The influence of pretreatment with oestradiol dipropionate (E) on the response of the rat testis to radiation has been studied. Treatment of rats for 3 weeks with E (100 mg/kg per week) induced severe atrophy of the testis. At this time, the testes were locally irradiated to doses of 0, 4 or 15 Gy, E treatment was continued for a further week and the rats were killed 24 or 36 weeks later. Radiation alone had a marked effect on spermatogenesis as assessed by testicular weight and counts of regenerating tubule cross-sections. At 24 weeks, 8% of cross-sections were found to possess spermatogenic cells after 4 Gy and this had increased to 15% at 36 weeks. No significant regeneration was observed after 15 Gy. Similar results were obtained in those rats pretreated with E. Following irradiation alone, decreases in interstitial cell numbers and testicular luteinizing hormone (LH) receptors reflected Leydig cell damage. Again, pretreatment with oestrogen did not appear to reduce Leydig cell damage. The results of the present study suggest that pretreatment with oestrogen is not able to reduce the testicular damage induced by moderate to high single doses of radiation.

Changes of oestrogen receptor levels in Leydig cells from mice and rats during culture

Two functional properties of Leydig cells in culture, i.e. LH-stimulated steroidogenesis and nuclear oestrogen receptor levels have been investigated. Leydig cells isolated from testes of immature rats and mature mice maintained their responsiveness to LH during 48-72 h of cell culture, although the mouse Leydig cells appeared to be less responsive to LH after 72 h of culture. In contrast, nuclear oestrogen receptor levels in both types of Leydig cells declined to 10-20% of the initial value after 24 h in culture. In the 48-72 h culture period nuclear oestrogen receptor levels recovered to 75% of the initial value only in Leydig cells from immature rats, whereas the nuclear oestrogen receptor levels in Leydig cells from mature mice remained low. These data demonstrate that during in vitro culture of Leydig cells, preservation of LH responsiveness does not necessarily warrant that other Leydig cell parameters e.g. nuclear oestrogen receptors also remain unaltered.

Testicular steroidogenic response to human chorionic gonadotropin of fifteen male transsexuals on chronic estrogen treatment

Fifteen transsexuals were prepared for surgery with estrogen treatment. The response to human chorionic gonadotropin (hCG) in the untreated state was similar to that of normal subjects when testosterone (T), estradiol-17 beta (E2), 17 alpha-hydroxyprogesterone (17 alpha-OHP), progesterone (P), 4-androstenedione (delta 4A), and dehydroepiandrosterone (DHA) were used as indices. Following estrogen therapy, plasma T, 17 alpha-OHP, and DHA levels were markedly reduced whereas delta 4A and P were not. In spite of the suppressive effects of estrogen, a good response to hCG was noted in such subjects in plasma levels of T, 17 alpha-OHP, and, to a lesser extent, delta 4A even after estrogen administration for 24 months. The high rates of 17 alpha-OHP to T induced by estrogen treatment is restored to normal by the administration of hCG.

Ontogenic relationships between two estrogen binding moieties in the male rat: alpha-fetoprotein and the testicular cytoplasmic estrogen receptor

The estrogen binding characteristics of rat alpha-fetoprotein (AFP) and the testicular cytoplasmic estrogen receptor (E2R) and the ontogenic relationships between these two estrogen binding moieties were investigated. Sucrose gradient sedimentation analysis revealed that AFP migrated as a single 4.6S peak whereas the receptor migrated as a single peak in the 8-9S region. Scatchard analyses of the binding data demonstrated high-affinity (10(8) M-1), high-capacity (450 pmol/mg protein) binding sites for AFP-estradiol and high-affinity (10(10) M-1), low-capacity (16 fmol/mg protein) binding sites for receptor-estradiol. Estradiol binding in serum (AFP) was high at birth, declined during the first 2 weeks and fell to low levels during the fourth week of life. In contrast, the testicular E2R was not detectable before day 21, rose after day 23, and reached adult concentrations by day 35. The inverse pattern suggested a relationship between the disappearance of AFP and the appearance of the receptor. However, in vivo administration of Dexamethasone, which resulted in a precocious decrease in AFP levels, had no effect on the ontogeny of the receptor. The ontogenic patterns of these two estrogen binding moieties may determine the onset of testicular sensitivity to estrogens.

The effect of delta 1-testolactone on serum testosterone and estradiol in the adult male rat

delta 1-Testolactone, an androgen derivative without intrinsic hormonal action, is known to block the aromatization of androgens to estrogens. This study was designed to assess its effect upon serum testosterone (T) and estradiol (E2) in the adult male rat. By itself, testolactone (TL) did not affect T/E2 levels in the dosages utilized. Daily injections of human chorionic gonadotropin (hCG) for 15 days caused a tenfold rise in serum T, although there was no increase in serum E2. When given along with hCG, TL did not alter the Leydig cell response. However, pretreatment of animals with TL increased the testicular response to hCG over that of saline-treated animals. Studies were also carried out to delineate the sources of estrogen in the adult male rat. These experiments demonstrate that (1) the majority of E2 is not testicular in origin but is derived from the adrenal; (2) the conversion of androgen precursors to E2 in the rat is not affected by TL; and (3) in spite of no demonstrable inhibition of E2 production, TL causes an increased Leydig cell responsiveness to hCG.

Estradiol benzoate induced changes in protein synthesis and lysosomal hydrolases in the pituitary of male rats

In vitro protein synthesis, lysosomal hydrolases activity and peroxidase activity in the anterior pituitary were estimated in adult male rats treated with 50 micrograms of estradiol benzoate (EB) for 1 day or 7 days. Pituitary protein synthesis, protein and RNA content increased after 7 days. A significant increase in total and membrane-bound acid phosphatase was noted after 1 day or 7 days of EB treatment whereas total beta-glucuronidase activity decreased in both 1 and 7 day group. Cathepsin activity increased after 7 days and pituitary peroxidase system did not change by EB treatment. These findings suggest that immediate change in the enzyme milieu may be one of the first reactions by which EB expresses its feedback control.

Direct inhibitory effect of estrogen on LH-stimulated androgen synthesis by ovarian cells cultured in defined medium

The direct inhibitory effect of estrogen on ovarian androgen synthesis was investigated. When primary cultures of rat ovarian theca-interstitial cells were grown in defined medium with LH there was a marked increase in androgen synthesis of which 98% was androsterone (control = 11 +/- 2 ng; LH = 1219 +/- 217 ng/ml/10(6) cells). Diethylstilbestrol (DES), estrone (E1), estradiol (E2), and estriol (E3) inhibited LH-stimulated androsterone synthesis by 81%, 81%, 81%, and 47%, respectively. The ED50's of the estrogens were: DES = 4.2 +/- 2.1 X 10(-9) M; E1 = E2 = 9.5 +/- 2.4 X 10(-8) M; and E3 = 3.8 +/- 2.6 X 10(-7) M. The estrogen effect was very rapid (t1/2 = 10 min) and long-lasting. Metabolic studies revealed that estrogen inhibited androsterone, androstenedione, 5 alpha-androstane-3 alpha, 17 beta-diol, and testosterone accumulation by 80%, dehydroepiandrosterone and 17 alpha-hydroxypregnenolone by 40%, 17 alpha-hydroxyprogesterone by 30%, while pregnenolone and progesterone were unchanged. These results prove, for the first time, that estrogen can directly inhibit LH-stimulated androgen production in ovarian theca-interstitial cells and suggest that mechanism involves, at least in part, a rapid selective inhibition of the 17 alpha-hydroxylase/C17-20 desmolase activities.

The effect of estrogen on Sertoli cell function

This study describes the use of adult rats as a model to determine whether chronic estrogen treatment irreversibly alters the capacity of Sertoli cells to secrete androgen binding protein (ABP). Twenty-five adult rats were implanted with silastic tubing containing 17 beta-estradiol. After 1 month of estradiol the epididymides had regressed to 47 per cent of the weight of the epididymides in a control group. The amount of ABP in control epididymides was 9.9 fmol./mg. protein, whereas no ABP was detectable in those from rats treated with estradiol for 1 month. Serum testosterone levels had been depressed by 90 per cent. Estradiol treatment for 8 months resulted in a 60 per cent lower body weight and a 91 per cent decrease in testicular weight compared to control animals. During this period the epididymides regressed significantly. When Sertoli cells were cultured from the testes of the estradiol implanted rats, in spite of the dramatic changes which had occurred in the testes, within 4 days the cultured cells synthesized ABP in response to FSH and testosterone. Furthermore, the direct addition of estrogen at a concentration of 200 ng./ml. to rat Sertoli cell cultures failed to depress ABP below control levels. Thus, although estradiol depresses ABP synthesis in vivo, probably through its depression of both gonadotrophin secretion and testosterone biosynthesis, it has no direct effect on the Sertoli cells, and its long-term inhibition of ABP synthesis by an indirect mechanism is reversible.

The aging Leydig cell: VII. Cytoplasmic estradiol receptors

Plasma estradiol and cytosolic estradiol receptor levels of testes were determined in a group of young (2-3 months) and old (24 months) Sprague-Dawley rats. Estradiol binding sites for the young rats averaged 5.6 +/- 0.3 fmol/mg protein (x +/- SE, n=12), which was comparable to that of the old rats, 5.7 +/- 0.3 fmol/mg protein (n=12). Using Scatchard analyses, the association constants at equilibrium of estradiol receptor binding of the old and young rats were the same, 6.1 x 10 10 M-1. Plasma estradiol levels were also similar in both groups-19.6 +/- 2.8 pg/ml (n=14) for the young and 19.2 +/- 2.6 pg/ml (n=10) for the old rats. Our results suggest that impaired testosterone biosynthesis in old rats was not due to elevated plasma estradiol levels or to differences in testicular estradiol receptor content.

Spermatic and peripheral oestradiol levels in patients affected by azoospermia due to seminiferous tubular damage

Plasma levels of testosterone, androstenedione and oestradiol were determined in the spermatic venous blood of both testes of 17 patient affected by azoospermia due to tubular damage (Group I). The results were compared with those found in 5 patients affected by azoospermia of obstructive origin and 5 patients with an inguinal hernia (Group II). Mean spermatic levels of testosterone and androstenedione were not significantly different in the two groups, while the mean (+/- SE) oestradiol spermatic level was significantly higher in patients of Group I (5.02 +/- 0.75 nM/l vs. 2.20 +/- 0.365 nM/l; P less than 0.05). Moreover, while the testosterone/androstenedione and the androstenedione/oestradiol ratios were not significantly different in the two groups, the mean (+/- SE) testosterone/oestradiol ratio was significantly lower in patients of Group I (552.71 +/- 80.94 vs. 939.86 +/- 129.45; P less than 0.025). Peripheral testosterone and androstenedione mean levels were not significantly different between the two groups while the mean peripheral oestradiol level (+/- SE) was significantly higher in Group I (0.107 +/- 0.021 nM/l vs. 0.038 +/- 0.05 nM/l; P less than 0.025). Peripheral oestradiol was not significantly related to peripheral FSH, nor to spermatic oestradiol in both groups. These results suggest the possibility that oestradiol may be involved in the pathogenesis of some cases of male infertility.

Direct inhibition of rat leydig cell function by tamoxifen

The effects of tamoxifen on rat testicular steroidogenesis were studied using dispersed interstitial cells. Tamoxifen significantly inhibited LH-, and 8-bromo-adenosine 3',5'-monophosphate (8-bromo-cyclic AMP)-stimulated testosterone synthesis in a dose-dependent manner. Tamoxifen (10(-5)M) also reduced LH-stimulated cyclic AMP formation. The addition of equimolar concentrations of 17 beta-estradiol or tamoxifen separately to interstitial cells resulted in similar inhibition of LH-stimulated testosterone synthesis. When equimolar concentrations of 17 beta-estradiol and tamoxifen were added concomitantly to interstitial cells, the inhibition was additive. Present studies demonstrate that tamoxifen has direct inhibitory effects on testicular steroidogenesis: both at the plasma membrane resulting in decreased cyclic AMP formation and also at steps subsequent to cyclic AMP.

Morphological pattern elicited by agents affecting spermatogenesis by stimulation

A variety of agents (clomiphene citrate, cyproterone acetate, estradiol 17-beta, medrogestone, medroxyprogesterone, and methoxychlor) thought to disrupt the normal pathway by which hormones stimulate the testis were tested in rats to determine the early morphologic changes in the testis. After initial trial experiments at which dose and sacrifice intervals were determined, the earliest morphological abnormalities were assessed quantitatively and related to the particular spermatogenic stage in which these defects were initiated. All agents tested produced an identical morphological pattern of response displaying a significant increase in Stage VII degenerating cells (pachytene spermatocytes, step 7 and step 19 spermatids) as compared with vehicle-administered rats. The number of degenerating cells in other stages did not significantly change. The rise in degenerating cells in Stage VII, as seen in this study, was similar to that reported in Russell and Clermont (1972) utilizing hypophysectomized rats, and that reported by other investigators who have used a variety of agents to disrupt the hormonal stimulation of the seminiferous tubules. The data indicate that no matter how, or at what level the hormonal stimulation of the testis is interrupted, the morphological pattern of response is the same, and that such a pattern is useful in predicting the mechanism of action of agents suspected of interfering with hormone action.

Ultrastructural study of Sertoli cells in rat seminiferous tubules during intrauterine life and the postnatal period

Sertoli cells have various functions: mechanical (creation of two compartments in the seminiferous tubules, migration of germinal cells), secretory (secretion of anti-Müllerian hormone, inhibin, androgen-binding-protein and estrogen) and phagocytic. We report an ultrastructural study of the rat Sertoli cell during maturation and consider possible correlations between the acquisition of certain morphological characteristics and certain functions. During fetal life, the Sertoli cell possesses differentiated zones of junction with the gonocytes and seems to have a role in the migration of the gonocytes towards the periphery of the seminiferous tubule. The Sertoli cell performs the phagocytosis of the gonocytes which degenerate during their migration, and seems to be the site of production of protein granules, whose presence can be related to the synthesis of anti-Müllerian hormone. After birth and before puberty, when the inclusions resembling secretory granules disappear, the Sertoli cell membranes in contact with spermatocytes II and spermatids differentiate, forming, through the differentiated junctional complexes, two compartments (adluminal and luminal) in the seminiferous tubules. Finally, they acquire the characteristics of active secretory cells, capable, in particular, of steroid synthesis.

Inhibition by estradiol-17 beta of porcine thecal androgen production in vitro

Thecal preparations from medium-sized procine ovarian follicles (3.5-5 mm diameter) were incubated for 4 h in a chemically defined medium in the presence or absence of highly purified luteinizing hormone (LH) and/or estradiol-17 beta (estradiol). LH (1 microgram/ml) stimulated the thecal production of testosterone (T) and dihydrotestosterone (DHT) by 2- to 3-fold. Although estradiol (10 microgram/ml) alone had only a slight but non-significant inhibitory effect on basal testosterone production, it significantly inhibited the production of both T and DHT as well as decreasing the DHT/T ratio in a dose-related manner in the presence of LH. Production of cyclic adenosine 3',5'-monophosphate (cAMP) and progesterone by the thecal cells was stimulated 50-to 200-fold and 2.5-fold, respectively, by LH. Estradiol had no significant effect on thecal cAMP and progesterone production in the presence or absence of the gonadotropin. These findings are consistent with the concept that estradiol produced by granulosa cells following hormonal stimulation may serve as a local negative feedback mechanism to control thecal androgen production.

Evidence for Leydig cell dysfunction in rats with seminiferous tubule damage

To study the effects of seminiferous tubule damage on Leydig cell function and morphology, rats were treated by fetal irradiation (to induce Sertoli cell-only syndrome, SCO), 3 months administration of hydroxyurea (HU), or chronic feeding of a vitamin A-deficient diet (VAD). Leydig cell function was assessed by the measurement of serum LH and testosterone and the response of serum testosterone to hCG stimulation, while morphology was studied by electron microscopy after perfusion fixation. Serum LH was significantly elevated in each experimental group, while basal serum testosterone was significantly lower only in SCO rats. In all treatment groups, the serum testosterone response to hCG was significantly decreased when measureed as the area under the response curve. Despite a decreased response to hCG, the Leydig cells were larger than normal and showed striking increases in quantities of smooth endoplasmic reticulum, mitochondria and Golgi complex. Leydig cell dysfunction has been demonstrated in animals with varying degrees of seminiferous tubule damage, but paradoxically the cytological features of the Leydig cells were indicative of hypertrophy.

Steroid and FSH action on LH receptors and LH-sensitive testicular responsiveness during sexual maturation of the rat

This study examines the effect of FSH, testosterone and estradiol on testicular LH receptors and in vitro testicular responsiveness to LH in immature rats under various conditions. FSH treatment of 15-day-old immature rats significantly increased the number of LH receptors but did not alter testicular responsiveness. FSH treatment of hypophysectomized immature rats increased the number of LH receptors and markedly increased testicular responsiveness. Treatment of hypophysectomized rats with testosterone proprionate for 4 days, followed by a 5-day treatment with FSH, enhanced the effect of FSH on the number of LH receptors but did not increase the effect of FSH on testicular responsiveness. In contrast, treatment with estradiol for 4 days before FSH treatment had no effect on the FSH-induced increase in LH receptors but completely inhibited the FSH-induced increase in testicular responsiveness. These observations suggest that during male sexual maturation (1) regulation of LH receptors is distinct from regulation of testicular responsiveness to LH, (2) estradiol may be a factor in the regulation of testicular responsiveness to LH, and (3) testosterone may enhance the FSH-induced increase of LH receptors.

Effect of estradiol benzoate on the pituitary-gonadal axis in the intact male rat

Adult male rats were treated with 50 microgram of estradiol benzoate daily for 28 days. The sex organs and pituitary weights showed changes classically associated with estrogen treatment. Both plasma and testicular testosterone levels diminished to almost trace level 24 hours after the first estrogen injection and remained at that level throughout the experimental period. The pituitary LH levels and concentration showed a progressive decline; however, the plasma LH levels remained unchanged throught the experimental period. These findings suggest that in intact adult males, estrogen affects testicular testosterone production directly. These observation suggests the necessity for reevaluation of the current concepts concerned with testis-pituitary feedback mechanisms.

Cannabinoids inhibit testosterone secretion by mouse testes in vitro

Addition of delta-9-tetrahydrocannabinol or cannabinol to an incubation medium containing decapsulated mouse testes caused a significant reduction in the accumulation of testosterone in the medium. This result suggests that the reported effects of cannabis on male sexual and reproductive function may result from direct inhibition of testicular steroidogenesis by both psychoactive and nonpsychoactive constituents of marihuana.

In vitro steroid metabolic studies in human testes I: Effects of estrogen on progesterone metabolism

A technique of incubation of testicular tissue in vitro with radiolabeled precursors was applied in the investigation of the steroid biosynthesis by testes of four young men after long-term, high-dose estrogen treatment. A positive correlation between plasma and testicular steroid levels, and in vitro capacity of the testes to metabolize progesterone was demonstrated. Estrogen administration produced a very significant inhibition of plasma and testicular levels of testosterone. The in vitro synthesis of testosterone from progesterone was very severely impaired; especially 17alpha-hydroxylation of progesterone. 20alpha-hydroxysteroid-dehydrogenase activity was found to be increased after estrogen treatment, both in vivo and in vitro. These findings suggest that testicular 17alpha-hydroxylase activity (and possibly also 17-20 lyase activity) is either under gonadotropin regulation, or is directly suppressed by estrogen. This could result by decreased enzyme synthesis, direct enzyme inhibition or affectation of the cofactors or cytochromes necessary for the enzymatic activity. 20alpha-reduction of C21-steroids would represent an alternative pathway for their catabolism, not regulated by gonadotropin or not affected by estrogen, that would be significant in situations with reduced 17alpha-hydroxylase activity.

Hormonal regulation of LH stimulation of testosterone production in isolated Leydig cells of immature rats: the effect of hypophysectomy, FSH, and estradiol-17beta

Testosterone production in isolated Leydig cells from testes of immature and adult rats was stimulated by addition of LH in a dose dependent way. Hypophysectomy of adult rats had no influence on LH-stimulated testosterone production in isolated Leydig cells after 5 days. In contrast hypophysectomy of immature rats resulted after 5 days in an almost complete loss of LH sensitivity of isolated Leydig cells. Daily adminitration of FSH during 5 days starting immediately after hypophysectomy maintained LH responsiveness of isolated Leydig cells of immature rats. Also FSH administration starting on day 5 after hypophysectomy resulted in a restoration of LH responsiveness. Estradiol benzoate, injected simultaneously with FSH, abolished the FSH-induced LH responsiveness.

The in-vitro and in-vito effects of diethylstilbestrol on testicular synthesis of testosterone

The effect of diethylstilbestrol (DES) on the percent conversion of a 14C-progesterone (14C-P) substrate to 14C-testosterone (14C-T) when added to incubates fo rat testicular homogenates has been measured. Similarly the effect of DES administered parenterally to intact adult rats at 9 dose regimens on such conversion has been evaluated. In addition, in the latter group serum luteinizing hormone (LH) levels were assessed simultaneously. DES added in-vitro significantly reduced T formation at every level. Only the large parenteral dose of DES affected T synthesis after 24 hours, while every parenteral dose significantly reduced T synthesis with 4 and 8 day regimens. Mean serum LH levels failed to reflect a significant decrease at the 1 and 4 day dose level, but did decrease significantly in 2 of 3 groups on the 8 day regimen. These results suggest that there is a direct effect of DES at a testicular level inhibiting T synthesis not associated with a simultaneous drop in mean serum LH levels. A measurable decrease in LH concentration does occur with continued treatment.

Plasma testosterone response to short-term human chorionic gonadotropin administration in men with follicle-stimulating hormone suppressed by exogenous estrogen

In order to investigate the role of FSH in Leydig cell function, six men were given four daily injections of HCG (4,000 IU) while receiving oral ethinyl estradiol. The peak testosterone levels in these subjects were contrasted to the results obtained in seven men who received HCG without additional exogenous steroid treatment. Urinary and plasma FSH was suppressed to 26% and 50%, respectively, of basal values by the estrogen treatment. Peak plasma testosterone determinations following HCG did not differ in the two groups of subjects. Additionally, an early pubertal boy had a normal HCG-induced testosterone rise while his urinary FSH was suppressed by estradiol to lower than prepubertal levels. The data indicate the short-term FSH suppression does not alter testicular responsivity to short-term HCG administration. A role for FSH in Leydig cell testosterone production in men has yet to be demonstrated.