Combined nestorone-testosterone gel suppresses serum gonadotropins to concentrations associated with effective hormonal contraception in men.

BACKGROUND: Novel male-based contraceptives are needed to broaden family planning choices. A progestin, Nestorone® (Nes) gel, plus a testosterone (T) gel suppresses sperm concentrations to levels associated with effective contraception in normal men. However, administration of two gels on different parts of the body daily is impractical. OBJECTIVE: Compare the effectiveness of daily application of a single, combined 8.3 mg Nes-62.5 mg T gel (Nes-T) vs. 62.7 mg T gel to suppress serum FSH and LH concentrations to ≤1.0 IU/L (a threshold associated with suppression of sperm concentrations to ≤1 million and effective contraception) and to compare the pharmacokinetics of serum Nes and T concentrations between the gel groups. DESIGN: We conducted a 28-day, double-blind, controlled trial of 44 healthy men randomized to daily Nes-T or T gel with measurement of hormones at baseline, treatment, and recovery and during 24-h pharmacokinetic studies on days 1 and 28 of treatment. RESULTS: Of the subjects who met pre-defined inclusion criteria, 84% of the Nes-T group suppressed serum gonadotropin concentrations to ≤1.0 IU/L at days 21-28 vs. 16.7% in the T group (p < 0.001). On day 1, Nes concentrations rose significantly above baseline by 2 h and continued to rise up to 24 h after Nes-T gel application. Nes concentrations were not detectable in the T group. Serum total T concentrations rose and were significantly higher in the T gel group compared to the Nes-T group at 24 h on day 1 and days 11, 14, and 21 (p < 0.01). There were no serious adverse events in either group. About 80% of the subjects reported satisfaction with both gels. CONCLUSION: Daily Nes-T gel effectively and safely suppresses serum gonadotropins and is acceptable to most men. It should be studied further in efficacy trials of hormonal male contraception.

Preventing secondary exposure to women from men applying a novel nestorone/testosterone contraceptive gel.

BACKGROUND: Testosterone (T)/Nestorone (NES) combination gel is a potential transdermal male contraceptive that suppresses gonadotropins and spermatogenesis. Transfer of transdermal T from men to women can be prevented by washing or covering application sites with clothing. OBJECTIVES: We hypothesized that showering or wearing a shirt over gel application sites would prevent secondary exposure of T and NES to a woman after close skin contact. MATERIALS AND METHODS: Twelve healthy male and 12 healthy female participants were recruited. Men applied T/NES 62 mg/8 mg gel to their shoulders and upper arms. Two hours after application, female partners rubbed the application site for 15 min. Exposure in the female partner was assessed under three conditions: a shirt covered the application site; the man showered prior to skin contact; or without intervention to reduce transfer. Serum T and NES concentrations were measured by LC-MS/MS in serial blood samples for 24 h after gel exposure. MAIN OUTCOMES: Change in female serum T and NES levels as measured by average concentration over 24 h (Cavg ). RESULTS: Median female serum T Cavg was 23.9 ng/dL (interquartile range, 19.3, 33.9) with the shirt barrier and 26.7 ng/dL (20.7, 33.9) after showering, which was higher than baseline 20.9 ng/dL (16.7, 25.0), both p < 0.03) but lower than without intervention (58.2 ng/dL [30.9, 89.1], both p < 0.01). Female serum NES Cavg and maximum concentration were below the lower limit of quantification with the shirt barrier and after showering, but increased without intervention in six of 12 women (maximum concentration <60 pg/mL). Men had lower average serum NES levels after showering (47 pg/ml [20, 94] compared to no intervention (153.3 pg/mL [51, 241], p < 0.02). CONCLUSION: Secondary transfer of T and NES occurs after intensive skin contact with the gel application site. Secondary transfer is decreased by a shirt barrier or showering before contact.

Reinitiation of sperm production in gonadotropin-suppressed normal men by administration of follicle-stimulating hormone.

The specific roles of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in controlling human spermatogenesis are poorly understood. We studied the effect of an experimentally induced, selective LH deficiency on sperm production in normal men. After a 3-mo control period, five men received 200 mg testosterone enanthate (T) i.m./wk to suppress LH, FSH, and sperm counts. Then, while continuing T at the same dosage, human FSH (hFSH) was administered simultaneously to replace FSH activity, leaving LH activity suppressed. Four men received 100 IU hFSH s.c. daily plus T (high dosage hFSH) for 13-14 wk, while one man received 50 IU hFSH s.c. daily plus T (low dosage hFSH) for 5 mo. The effect on sperm production of the selective LH deficiency produced by hFSH plus T administration was assessed. In the four men who received the high dosage hFSH regimen, sperm counts were markedly suppressed during T administration alone (0.3+/-0.2 million/cm(3), mean+/-SE, compared with 94+/-12 million/cm(3) during the control period). Serum LH bioactivity (determined by in vitro mouse Leydig cell assay) was suppressd (140+/-7 ng/ml compared with 375+/-65 ng/ml during control period) and FSH levels (by radioimmunoassay) were reduced to undetectable levels (<25 ng/ml, compared with 98+/-21 ng/ml during control period) during T alone. With the addition of 100 IU hFSH s.c. daily to T, sperm counts increased significantly in all subjects (33+/-7 million/cm(3), P < 0.02 compared with T alone). However, no subject consistently achieved sperm counts within his control range. Sperm morphology and motility were normal in all four men and in vitro sperm penetration of hamster ova was normal in the two men tested during the hFSH-plus-T period. During high-dosage hFSH administration, serum FSH levels increased to 273+/-44 ng/ml (just above the normal range for FSH, 30-230 ng/ml). Serum LH bioactivity was not significantly changed compared with the T-alone period (147+/-9 ng/ml). After the hFSH-plus-T period, all four men continued to receive T alone after hFSH was stopped. Sperm counts were again severely suppressed (0.2+/-0.1 million/cm(3)), demonstrating the dependence of sperm production on hFSH administration. Serum T and estradiol (E(2)) levels increased two- to threefold during T administration alone compared with the control period. Both T and E(2) levels remained unchanged with the addition of hFSH to T, confirming the lack of significant LH activity in the hFSH preparation. In the one man who received low dosage hFSH treatment, sperm counts were reduced to severely oligospermic levels, serum FSH was suppressed to undetectable levels, and serum LH bioactivity was markedly lowered during the T-alone period. With the addition of 50 IU hFSH s.c. daily to T, sperm counts increased, to a mean of 11+/-3 million/cm(3). During this period, serum FSH levels increased to a mean of 105+/-11 ng/ml (slightly above this man's control range and within the normal adult range), while LH bioactivity remain suppressed. After hFSH was stopped and T alone was continued, sperm counts were again severely reduced to azoospermic levels. We conclude that FSH alone is sufficient to reinitiate sperm production in man during gonadotropin suppression induced by exogenous T administration. FSH may stimulate sperm production in this setting by increasing intratesticular T through androgenbinding protein production or by increasing the sensitivity of the spermatogenic response to the intratesticular T present during exogenous T administration.

Follicle-stimulating hormone and human spermatogenesis.

The role of follicle-stimulating hormone (FSH) in the control of spermatogenesis is not well established in any species, including man. We studied the effect of an experimentally-induced, selective FSH deficiency on sperm production in normal men. After a 3-mo control period, five normal men received testosterone enanthate (T) 200 mg i. m. weekly to suppress luteinizing hormone (LH) and FSH, until three successive sperm counts revealed azoospermia or severe oligospermia (sperm counts <3 million/ml). Then, while continuing T, human chorionic gonadotropin (hCG) 5,000 IU i. m. three times weekly was administered simultaneously to replace LH activity, leaving FSH activity suppressed. The effect of the selective FSH deficiency produced by hCG plus T administration on sperm production was determined. Sperm counts (performed twice monthly throughout the study) were markedly suppressed during T administration alone (1.0+/-1.0 million/ml mean+/-SE, compared with 106+/-28 million/ml during the control period, P < 0.001). With the addition of hCG to T, sperm counts returned toward normal (46+/-16 million/ml, P < 0.001 compared with T alone). In two subjects, sperm counts during hCG plus T returned into the individual's control range. Sperm motility and morphology were consistently normal in all men during hCG plus T. Serum FSH levels by RIA were normal (110+/-10 ng/ml) in the control period and were suppressed to undetectable levels (<25 ng/ml) in the T alone and hCG plus T periods. Urinary FSH excretion was markedly suppressed in the T alone (60+/-15 mIU/h-2nd IRP, P < 0.01) and hCG plus T (37+/-9 mIU/h, P < 0.01) periods compared with the control period (334+/-78 mIU/h). We conclude that spermatogenesis as assessed by sperm counts, motilities, and morphologies may be reinitiated and maintained at normal levels in men with undetectable blood FSH levels and urinary excretion of FSH less than that of prepubertal children. This conclusion implies that, although FSH may exert effects on human testicular function, maintenance of normal spermatogenesis and reinitiation of sperm production after short-term suppression by exogenous steroids can occur in spite of nearly absent FSH stimulation.

Relative roles of follicle-stimulating hormone and luteinizing hormone in the control of inhibin secretion in normal men.

The glycoprotein hormone inhibin is produced by the Sertoli cells of the testis under the influence of follicle-stimulating hormone (FSH) and is postulated in turn to inhibit FSH secretion. Luteinizing hormone (LH) is not recognized to have an important role in the control of inhibin secretion in any species. To determine the relative roles of FSH and LH in the control of inhibin secretion in man, we examined the effects of selective FSH and LH replacement on serum inhibin levels in normal men whose endogenous gonadotropins were suppressed by testosterone (T). After a 3-mo control period, nine men received 200 mg T enanthate i.m. weekly for 3-9 mo. During T treatment, serum LH and FSH levels were markedly suppressed and serum inhibin levels fell to 40% of control values. While continuing T, 3-5 mo of treatment with purified hFSH (n = 4) or hLH (n = 4) increased the respective serum gonadotropin level into the upper normal range and significantly increased inhibin levels back to 64 and 55% of control values, respectively. Supraphysiological LH replacement with high doses of human chorionic gonadotropin (n = 3) returned serum inhibin levels to 63% of control values. In no case did inhibin levels return fully to control levels. In conclusion, serum inhibin levels fell during gonadotropin suppression and were partially and approximately equally restored by either FSH or LH treatment. FSH presumably acts directly on the Sertoli cell to increase inhibin secretion whereas LH may act via increases in intratesticular T levels and/or other factor(s).

Comparison of the single dose pharmacokinetics, pharmacodynamics, and safety of two novel oral formulations of dimethandrolone undecanoate (DMAU): a potential oral, male contraceptive.

Dimethandrolone (DMA, 7α,11ß-dimethyl-19-nortestosterone) has both androgenic and progestational activities, ideal properties for a male hormonal contraceptive. In vivo, dimethandrolone undecanoate (DMAU) is hydrolyzed to DMA. We showed previously that single oral doses of DMAU powder in capsule taken with food are well tolerated and effective at suppressing both LH and testosterone (T), but absorption was low. We compared the pharmacokinetics and pharmacodynamics of two new formulations of DMAU, in castor oil and in self-emulsifying drug delivery systems (SEDDS), with the previously tested powder formulation. DMAU was dosed orally in healthy adult male volunteers at two academic medical centers. For each formulation tested in this double-blind, placebo-controlled study, 10 men received single, escalating, oral doses of DMAU (100, 200, and 400 mg) and two subjects received placebo. All doses were evaluated for both fasting and with a high fat meal. All three formulations were well tolerated without clinically significant changes in vital signs, blood counts, or serum chemistries. For all formulations, DMA and DMAU showed higher maximum (p < 0.007) and average concentrations (p < 0.002) at the 400 mg dose, compared with the 200 mg dose. The powder formulation resulted in a lower conversion of DMAU to DMA (p = 0.027) compared with both castor oil and SEDDS formulations. DMAU in SEDDS given fasting resulted in higher serum DMA and DMAU concentrations compared to the other two formulations. Serum LH and sex hormone concentrations were suppressed by all formulations of 200 and 400 mg DMAU when administered with food, but only the SEDDS formulation was effectively suppressed serum T when given fasting. We conclude that while all three formulations of oral DMAU are effective and well tolerated when administered with food, DMAU in oil and SEDDS increased conversion to DMA, and SEDDS may have some effectiveness when given fasting. These properties might be advantageous for the application of DMAU as a male contraceptive.

Male hormonal contraception: looking back and moving forward.

Despite numerous contraceptive options available to women, approximately half of all pregnancies in the United States and worldwide are unplanned. Women and men support the development of reversible male contraception strategies, but none have been brought to market. Herein we review the physiologic basis for male hormonal contraception, the history of male hormonal contraception development, currents agents in development as well as the potential risks and benefits of male hormonal contraception for men.

Norethisterone enanthate plus testosterone undecanoate for male contraception: effects of various injection intervals on spermatogenesis, reproductive hormones, testis, and prostate.

The goal of this study was to find the most favorable injection interval of norethisterone enanthate (NETE) plus testosterone undecanoate (TU) in terms of gonadotropin, sperm suppression, and prostatic effects. Fifty normal men were randomly assigned to receive NETE 200 mg plus TU 1000 mg every 8 wk (n = 10), every 12 wk (n = 10), every 6 wk for 12 wk and then every 12 wk (n = 10), and every 6 wk for 12 wk and thereafter TU 1000 mg plus placebo every 12 wk (n = 10), and placebo plus placebo every 6 wk for 12 wk and then every 12 wk (n = 10) for 48 wk. Semen analyses, blood drawings, physical examinations, and prostate ultrasounds were performed throughout the study. Of the men in the 8-wk injection group, 90% (nine of 10) achieved azoospermia, compared with 37.5% (three of eight) in the 12-wk injection group (P = 0.019). TU plus placebo injected every 12 wk did not maintain sperm suppression. Prostate volumes did not change significantly in either group. In conclusion, these data suggest that the combined administration of NETE and TU at 8-wk intervals represents an effective hormonal contraceptive regimen.

Newer agents for hormonal contraception in the male.

Efforts to create a hormonal contraceptive for men use testosterone to suppress the production of pituitary gonadotropins and, hence, spermatogenesis. However, conventional testosterone must be administered by frequent injection, and when given alone, is not 100% effective. Therefore, newer androgens and agents that synergistically suppress gonadotropin production are being studied to create an effective and commercially viable contraceptive.

Klinefelter syndrome.

Klinefelter syndrome is the most common sex chromosome disorder. Affected males carry an additional X chromosome, which results in male hypogonadism, androgen deficiency, and impaired spermatogenesis. Some patients may exhibit all of the classic signs of this disorder, including gynecomastia, small testes, sparse body hair, tallness, and infertility, whereas others, because of the wide variability in clinical expression, lack many of these features. Treatment consists of testosterone replacement therapy to correct the androgen deficiency and to provide patients with appropriate virilization. This therapy also has positive effects on mood and self-esteem and has been shown to protect against osteoporosis, although it will not reverse infertility. Although the diagnosis of Klinefelter syndrome is now made definitively using chromosomal karyotyping, revealing in most instances a 47,XXY genotype, the diagnosis also can be made using a careful history and results of a physical examination, with the hallmark being small, firm testes. As it affects 1 in 500 male patients and presents with a variety of clinical features, primary care physicians should be familiar with this condition.

Regulation of luteinizing hormone pulse frequency and amplitude by testosterone in the adult male rat.

Our objective was to gain a better understanding of the role of testosterone (T) in regulating the minute to minute dynamics of LH secretion in the adult male rat. To this end, we examined the patterns of blood LH levels in intact animals and evaluated the effect of small physiological doses of T on mean blood LH and FSH levels and on LH pulse frequency and amplitude in the castrate animal. The intact rat exhibited low frequency (period, approximately 145 min) and low amplitude (approximately 16 ng/ml) LH pulses. After castration, LH pulse frequency (period, approximately 20 min) and amplitude (approximately 118 ng/ml) increased dramatically over that of intact animals. T, administered to castrate rats through Silastic implants, caused a dose-dependent and parallel reduction in mean blood LH and FSH levels. The lowest T dose, which increased mean plasma T levels to 0.5 ng/ml above those of the sham-treated castrates, produced a significant reduction in LH pulse frequency, with a significant increase in pulse amplitude. The next highest T dose caused a reduction in pulse amplitude to a value significantly lower than that in the sham-treated castrates. The highest T dose, which produced steady state mean plasma T levels (approximately 1.6 ng/ml) less than the mean level of the intact group (approximately 2.2 ng/ml), caused a profound reduction in pulse frequency to lower than that of the intact group. These observations demonstrate that T can exert a complex, dose-dependent effect on LH secretory dynamics and imply that one important site of T-mediated negative feedback is the brain's LHRH pulse generator.

Immunohistochemical localization of androgen receptors in the rat testis: evidence for stage-dependent expression and regulation by androgens.

Androgens are essential for the maintenance of normal spermatogenesis in the rat. We assessed the sites, developmental pattern, and hormonal control of androgen receptors (AR) in the rat testis. Adult male rats were studied after 1) no treatment; 2) ethane dimethane sulfonate (EDS), which eradicates Leydig cells and endogenous testosterone (T); 3) EDS plus T replacement beginning at the time of EDS administration; or 4) methoxyacetic acid, which leads to the loss of specific germ cell types. Testes were also obtained from normal immature rats (aged 5, 14, 16, 21, 28, 31, 35, 38, and 45 days). After microwave antigen retrieval, immunohistochemistry was performed using a rabbit polyclonal antibody (Novocastra) raised against a peptide unique to the N-terminal region of the AR and detection with biotinylated swine antirabbit immunoglobulin G, avidin-biotin complex/alkaline phosphatase, and nitroblue tetrazolium salt (NBT)/5 bromo-4-chloro-3-indolylphosphate (BCIP) substrate. In adults, nuclear immunostaining of Sertoli cells (SC) increased progressively in intensity from stages II through VII of the spermatogenic cycle, and then declined precipitously during stage VIII to become barely detectable in stages IX-XIII. Prominent AR immunostaining was also evident in peritubular myoid cells, arterioles, and interstitial cells; staining in these cells did not vary with the stage of the cycle of the adjacent tubules. EDS caused a severe loss of AR immunostaining in all cell types. Replacement of T in EDS-treated animals resulted in a pattern of AR immunostaining comparable to that in controls, although staining intensity was reduced. Methoxyacetic acid administration did not affect the pattern of AR staining. In immature rats, peritubular myoid cell immunostaining was prominent from day 5; SC staining was detectable on day 5, increased in intensity with age, and became stage dependent between days 21-35. The following conclusions were reached. 1) Immunohistochemically detectable AR expression in SC occurs predominantly in stages II-VII of the spermatogenic cycle, with highest levels at stage VII. 2) AR immunostaining is also prominent in peritubular myoid cells, arterioles, and Leydig cells (but not in germ cells), but is unrelated to the stage of adjacent tubules. 3) Endogenous T and/or its metabolites control the expression of AR in the testis. 4) AR immunostaining is detectable by day 5 of age and becomes stage specific in SC between days 21-35.

Evidence for activation of the central nervous system-pituitary mechanism for gonadotropin secretion at the time of puberty in the male rat.

During sexual development in the male rat, serum testosterone (T) levels increase markedly at 45-60 days of age. At the time of the pubertal rise in T levels, activation of the hypothalamic-pituitary axis is difficult to demonstrate, since there is little change in serum LH levels and a decrease in serum FSH levels. We determined whether experimental maintenance of stable pubertal T levels in these animals as they passed through the normal age of puberty would allow demonstration of a major increase in serum gonadotropin levels. At 14-15 days of age, male rats were castrated and outfitted with either T-containing or empty Silastic capsules. Another group of rats was left intact and outfitted with empty capsules. At various times between 29 and 58 days of age, blood was drawn for measurement of serum LH, FSH, and T levels. In the T-implanted castrated rats, serum T levels were comparable to those in midpubertal intact rats, without significant differences among age groups. In this setting of stable T levels, serum LH and FSH were suppressed to levels at or below those in pubertal intact rats until 51 days of age, when they increased significantly into the untreated castrate range. In contrast, untreated castrate animals demonstrated markedly reduced serum T and elevated LH and FSH levels that did not change significantly throughout the entire study. In intact rats, serum T levels were stable until 58 days of age, when they increased over 2-fold; serum LH levels did not change significantly with age, and serum FSH levels decreased significantly by 54 days of age. A separate group of rats was castrated and outfitted with T-containing Silastic capsules at 21 days of age. In these animals, there were significant increases in hypothalamic LHRH, norepinephrine (NE), and dopamine levels and NE turnover rate at 56 compared to 36 days of age. We conclude that stable pubertal levels of T are able to suppress gonadotropin levels in castrated rats until the normal age of puberty, at which time LH and FSH levels increase markedly. This decrease in sensitivity of the hypothalamic-pituitary axis to T negative feedback at puberty is accompanied by increases in hypothalamic LHRH, NE, and dopamine levels and NE turnover rate. These results provide direct evidence for activation of the central nervous system-pituitary mechanism regulating gonadotropin secretion at puberty in the male rat.(ABSTRACT TRUNCATED AT 400 WORDS)

Diminished luteinizing hormone pulse frequency and amplitude with aging in the male rat.

Aging in the male rat is associated with a reduction in circulating testosterone levels. One possible cause of this decline is an age-related alteration of central nervous system-mediated LH secretion. To examine the effects of age on the hypothalamo-hypophyseal system, in the absence of gonadal steroid feedback, we studied the pattern of pulsatile LH secretion in castrate male Sprague-Dawley rats, aged 3 months (young), 8 months (middle-aged), and 26 months (old). All animals were castrated, and after 3 weeks, they were implanted with indwelling atrial catheters. One day later, duplicate 25 microliters blood samples were obtained at 4-min intervals for 4 h, while the animals were awake and unrestrained. Serum levels of LH, FSH, and testosterone were measured in animals before castration, and blood LH levels were measured in the postcastration, repeated sampling studies. After castration, middle-aged and old animals exhibited significantly lower mean serum LH levels, associated with a diminished amplitude of LH secretory episodes compared to young rats. In the oldest group, LH pulse frequency was significantly lower compared to middle-aged and young animals. Since the control of LH secretory episodes resides in the central nervous system, we propose that alterations in frequency of LH pulses observed in the aged, castrate male rat are the result of a diminished functional capacity of LHRH-containing neurons or of neurotransmitters that modulate their activity in the aging brain.

Follistatin decreases activin-stimulated FSH secretion with no effect on GnRH-stimulated FSH secretion in prepubertal male monkeys.

Follistatin is an activin-binding glycoprotein that decreases FSH secretion in vitro and in vivo in rats. The mechanism by which follistatin acts is unclear, but it has been suggested that it may bind endogenous activin and neutralize its effects. In this study, we wished to test the ability of follistatin to suppress FSH secretion in vivo in primates whose FSH secretion has been stimulated by activin or by GnRH. Six prepubertal male monkeys were injected intravenously with human recombinant follistatin at the dose of 90 micrograms/kg or 180 micrograms/kg plus activin (90 micrograms/kg) or GnRH (10 micrograms/kg). Frequent blood samples were drawn for 12 hours following each injection. Bio FSH and LH levels were measured in those samples. GnRH and activin each stimulated FSH bioactivity. Both doses of follistatin significantly inhibited the activin-induced increase in FSH (p < 0.05). The GnRH-induced increase in FSH was not affected by follistatin. LH levels were not affected by follistatin in any of the studies. These data suggest that follistatin can suppress the activin-induced increase in FSH in primates and is consistent with the hypothesis that follistatin can block the physiological effects of endogenous activin in primates. This effect is likely to be due to the binding of follistatin to activin either in the peripheral circulation or at the pituitary level.

Recombinant human activin-A stimulates basal FSH and GnRH-stimulated FSH and LH release in the adult male macaque, Macaca fascicularis.

Activin-A is a homodimer of the beta A inhibin subunit that stimulates FSH secretion by pituitary cells in vitro; however, the physiological relevance of this effect is unknown. We have examined whether recombinant human activin-A (activin-A; 80 micrograms/kg/day iv infusion for 50.5 h) has in vivo bioactivity in the adult male macaque (n = 5). Serum FSH and LH bioactivity and serum testosterone (T) levels were measured on 2 control days and after 24 and 48 h of activin-A administration. Basal FSH levels increased significantly (p less than 0.05) by 17% at 24 h and 82% at 48 h during activin-A administration. No changes in basal LH or T levels were seen. The FSH and LH responses to GnRH (5 micrograms/kg, iv bolus) increased significantly (p less than 0.05) by 117% and 55% after 48 h of activin-A, respectively. A small (16%), but statistically significant (p less than 0.05), increase in the T response to the GnRH challenge was also noted. These data are preliminary evidence in support of a physiological role for activin-A in the control of gonadotropin secretion in the male primate.

Modulation of pulsatile gonadotropin secretion by testosterone in man.

In experimental animals, primary testicular deficiency leads to increased LH pulse frequency. Pulsatile FSH secretion has not been well characterized in any species. To determine the effect of testosterone (T) on the pattern of pulsatile gonadotropin secretion in man, we performed frequent blood-sampling studies in six normal men and six men with primary hypogonadism. All primary hypogonadal men were studied 6-8 weeks after stopping T replacement therapy. Five of the six hypogonadal men were restudied 6-8 weeks after treatment with T enanthate (200 mg, im, every 2 weeks; sampling in this group was 2 weeks after their last T injection). Blood sampling was done at 10-min intervals for 12 h in all subjects, and the pattern of episodic LH and FSH secretion was determined. Normal men had a serum T level of 6.3 +/- 0.3 ng/ml (mean +/- SEM), a LH level of 34 +/- 3 ng/ml, and a LH pulse pattern characterized by low frequency (7.6 +/- 0.7 pulses/12 h) and low amplitude (16 +/- 1 ng/ml). Compared to normal men, primary hypogonadal men had a significantly lower T level (2.9 +/- 0.4 ng/ml) and significantly higher LH pulse frequency (13.0 +/- 1.3 pulses/12 h), amplitude (51 +/- 7 ng/ml), and mean level (222 +/- 26 ng/ml). Reinstitution of T replacement therapy in hypogonadal men resulted in a significant increase in the T level (4.7 +/- 0.5 ng/ml) and significant decreases in LH pulse frequency (7.2 +/- 1.6 pulses/12 h) and amplitude (41 +/- 5 ng/ml) as well as mean LH level (75 +/- 15 ng/ml). FSH levels fluctuated in a distinctly pulsatile pattern in all three groups. Differences in pulsatile FSH secretion between primary hypogonadal men before and during T therapy and normal men paralleled those in pulsatile LH secretion in both frequency and amplitude. These results demonstrate that in man 1) diminished T negative feedback results in high frequency (circhoral), high amplitude LH and FSH pulses; 2) T replacement decreased LH and FSH pulse frequency and amplitude as well as mean levels; and 3) the decreased LH and FSH pulse frequency with T treatment implies that T or a metabolite of T acts on the central nervous system to slow the hypothalamic LHRH pulse generator.

Gonadotropin-releasing hormone antagonist plus testosterone: a potential male contraceptive.

No effective hormonal contraceptive has yet been devised for men. Through their suppressive effect on gonadotropin secretion, GnRH antagonists inhibit both testosterone (T) production and spermatogenesis in animals. Long term administration of an antagonist alone would result in androgen deficiency; this would cause unacceptable physiological and behavioral sequellae in men. Therefore, androgen replacement must be included in any GnRH antagonist regimen used in human male contraception. We tested the hypothesis that the combination of a GnRH antagonist plus T would suppress spermatogenesis in the male primate to azoospermic levels while maintaining normal serum T levels. We examined the effects of the GnRH antagonist Deterelix [N-Ac-DNal(2)1-DpCl-Phe2-DTrp3-DhArg(Et2)6 -DAla10-GnRH], alone and with simultaneous T replacement, on sperm production and serum T levels in adult male monkeys (n = 22). After 12 weeks of daily sc antagonist injection, all animals that received antagonist alone (n = 5) and those that 750 micrograms/kg.day antagonist plus T (n = 5) were azoospermic. After 16 weeks, four of five animals that received 250 micrograms/kg.day antagonist plus T became azoospermic. Control animals (n = 7) received daily injections of vehicle; sperm counts increased somewhat during the study period in that group. Castrate range T levels were achieved in animals receiving antagonist alone. T levels in the groups that received T supplementation and in the control group were in the normal male range throughout the treatment period. Sperm counts returned to the pretreatment range in all animals during the recovery period. We conclude that the combination of a GnRH antagonist plus T can induce azoospermia reversibly in this nonhuman primates species, and that a similar combination may be an effective contraceptive regimen in men. The GnRH antagonist alone may be an effective treatment for androgen-dependent neoplasia.

Chronic human chorionic gonadotropin administration in normal men: evidence that follicle-stimulating hormone is necessary for the maintenance of quantitatively normal spermatogenesis in man.

The role of FSH in the maintenance of spermatogenesis in man is poorly understood. To determine whether normal serum levels of FSH are necessary for the maintenance of quantitatively normal spermatogenesis, we first studied the effect on sperm production of selective FSH deficiency induced by chronic administration of hCG in normal men. Then, we determined the effect of FSH replacement in some of these men. After a 3-month control period, eight normal men (aged 30-39 yr) received 5000 IU hCG, im, twice weekly for 7 months. Then while continuing the same dosage of hCG, subjects simultaneously received 200 mg testosterone enanthate (T), im, weekly for an additional 6 months. hCG administration alone resulted in partial suppression of the mean sperm concentration from 88 +/- 24 (+/-SEM) million/ml during the control period to 22 +/- 7 million/ml during the last 4 months of hCG treatment (P less than 0.001 compared to control values). With the addition of T to hCG, sperm counts remained suppressed to the same degree. Except for one man who became azoospermic while receiving hCG plus T, sperm motilities and morphologies remained normal in all subjects throughout the entire study. During both the hCG alone and hCG plus T periods, serum FSH levels were undetectable (less than 25 ng/ml), and urinary FSH levels were comparable to those in prepubertal children and hypogonadotropic hypogonadal adults. We replaced FSH activity in four of the eight men in whom prolonged selective FSH deficiency and partial suppression of sperm production were induced by hCG administration. Immediately after the period of hCG plus T administration, T was stopped in four men who continued to receive hCG alone (5000 IU, im, twice weekly) for 3 months. Then, while continuing the same dosage of hCG, these men received 100 IU human FSH, sc, daily (n = 2) or 75 IU human menopausal gonadotropin, sc, daily (n = 2) for 5-8 months. During the second period of hCG administration alone, serum FSH levels were undetectable (less than 25 ng/ml), and sperm concentrations were suppressed (34 +/- 13 million/ml) compared to the control values for these four men (125 +/- 39 million/ml; P less than 0.001). With the addition of FSH to hCG, FSH levels increased (213 +/- 72 ng/ml) and sperm concentrations rose significantly, reaching a mean of 103 +/- 30 million/ml (P less than 0.03 compared to hCG alone).(ABSTRACT TRUNCATED AT 400 WORDS)

Testosterone administration inhibits gonadotropin secretion by an effect directly on the human pituitary.

Testosterone (T) administration slows LH pulse frequency in man, presumably by an effect on the hypothalamic GnRH pulse generator, but it also may have a direct action on the pituitary. To determine if T does indeed affect gonadotropin secretion by acting directly on the pituitary, we studied the effect of T on GnRH-stimulated gonadotropin secretion. Six men with hypogonadotropic hypogonadism were treated with physiological doses of GnRH (5 micrograms every 2 h, sc by automatic infusion pump) for 6 weeks. Once their gonadotropin levels were normal, the men received a supraphysiological dosage of T enanthate (200 mg, im, weekly for 8 weeks) in addition to GnRH. They then received GnRH alone for a final 8-week period. Blood sampling was performed every 10 min for 8 h at the end of each of the three study periods. T administration suppressed the mean serum LH level to about 50% of the value during GnRH alone [18 +/- 2 (+/- SE) vs. 37 +/- 2 micrograms/L; P less than 0.05] and suppressed the mean serum FSH level to about 30% of the value during GnRH alone (39 +/- 6 vs. 128 +/- 28 micrograms/L; P less than 0.05). Eight weeks after stopping T, while continuing GnRH alone, serum LH and FSH levels were similar to those at the end of the first period of GnRH administration. The mean LH response to GnRH was reduced during T administration (17 +/- 3 micrograms/L) compared to that during the initial period of GnRH alone (31 +/- 4 micrograms/L; P less than 0.05). Serum T and estradiol levels were in the low normal range after GnRH alone before T administration (11 +/- 2 nmol/L and 105 +/- 17 pmol/L, respectively) and increased to just above the normal adult ranges after 8 weeks of T administration (36 +/- 5 nmol/L and 264 +/- 49 pmol/L, respectively). These results demonstrate that T and/or its metabolites inhibit LH and FSH secretion by a GnRH-independent mechanism, probably directly on the pituitary gland, in man.