Failure of high-dose sustained release luteinizing hormone releasing hormone agonist (buserelin) plus oral testosterone to suppress male fertility.

Previously we have demonstrated that sperm counts of normal young men decreased during constant subcutaneous infusion of the LHRH agonist buserelin (118 or 230 micrograms/d). In order to test whether azoospermia can be achieved with higher doses, seven young men received 450 micrograms buserelin subcutaneously daily for 12 weeks via extracorporeal osmotic minipumps. To avoid symptoms of androgen deficiency, oral supplementation with 80 mg/d testosterone undecanoate (TU) was initiated in week 5 and was increased to 120 mg/d by week 8. Follow-up after treatment lasted for another 12 weeks. In order to evaluate possible psychotropic effects of treatment-related endocrine changes, continuous psychometric testing was performed focusing on personality, emotions and sexuality. After an initial rise, both serum LH and FSH returned to normal. FSH was below normal during the 3rd-5th week following treatment. LHRH stimulation tests performed at the end of treatment showed pituitary desensitization. Serum T (always measured between 0800 and 1300 h at least 12 h after last TU) tended to decrease by week 7 and remained slightly depressed until the end of treatment while libido, potency and emotional well-being remained unchanged. While testicular volumes showed a reduction from week 7 of treatment to week 10 post-treatment, sperm counts decreased only insignificantly from 65 +/- 10 to 44 +/- 14 million per ml in week 12 post-treatment. Severe oligo- or azoospermia was not observed in any of the seven men. It is concluded that full androgen substitution by TU can drastically delay if not abolish the antifertility effect of LHRH-induced pituitary desensitization.

Reversible inhibition of testicular function by a gonadotropin hormone-releasing hormone antagonist in monkeys (Macaca fascicularis).

The potential of a gonadotropin-releasing hormone (GnRH) antagonist to inhibit reproductive functions in a male nonhuman primate (Macaca fascicularis) was evaluated. Continuous infusion of 2 mg/day of [N-Ac-D-Nal(2)1, D-pCl-Phe2, D-Trp3, D-hArg(Et2)6, D-Ala10]-GnRH (RS-68439) via osmotic minipumps for 9 weeks caused immediate and sustained reduction of serum luteinizing hormone and testosterone concentrations and led to azoospermia in three animals and to sperm counts less than 5 X 10(6) in a fourth. Testicular histology showed severe atrophy of Leydig cells and tubules. The endocrine parameters returned to normal within 2 weeks of termination of treatment. Seminiferous tubule function was restored 14 to 18 weeks after treatment, as indicated by normal ejaculate parameters. It is concluded that chronic GnRH antagonist treatment reversibly inhibits pituitary and testicular function in a nonhuman primate. GnRH antagonists may thus have a potential for clinical use in fertility control and in treatment of androgen-dependent tumors.

PIP: The potential of a gonadotropin-releasing hormone (GnRH) antagonist to inhibit reproductive functions in a male nonhuman primate was evaluated in the Macaca fascicularis monkey. The monkeys were chronically infused with a GnRH antagonist through subcutaneously implanted osmotic minipumps for 9 weeks; their pituitary and testicular functions were monitored throughout the study period. Single injections of 1.0, 2.5, and 5.0 mg of the antagonist in castrated monkeys caused an immediate and marked decrease in serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Suppression was so effective that with 7-9 weeks of the onset of treatment, azoospermia occurred in 3 of the 4 monkeys studied and extremely low sperm counts were measured in the 4th animal. Testicular histology showed severe atrophy of Leydig cells and tubules. The endocrine parameters returned to normal within 2 weeks of termination of treatment. Seminiferous tubule function was restored 14-18 weeks after treatment. It was concluded that chronic GnRH treatment reversibly inhibits pituitary and testicular function in a nonhuman primate and thus may have potential for use in fertility control and the treatment of androgen-dependent tumors.

Salivary testosterone levels in normal and testosterone treated monkeys.

Testosterone concentrations in saliva and matched serum samples were measured by radioimmunoassay, in normal and testosterone treated adult male cynomolgus monkeys (Macaca fascicularis) and in untreated rhesus monkeys (Macaca mulatta). Saliva and serum samples were collected under ketamine anaesthesia. In 4 cynomolgus monkeys, the mean basal testosterone levels were 195 +/- 22 pmol/l in saliva and 24 +/- 2 nmol/l in serum (n = 17). The salivary testosterone corresponded to 0.9 +/- 0.1% of the serum testosterone concentration. In 5 rhesus monkeys the mean testosterone concentrations were 147 +/- 10 pmol/l in saliva and 17 +/- 2 nmol/l in matched serum samples with a percent ratio of 1.6 +/- 0.3 (n = 15). Following a single i.m. injection of 50 mg testosterone propionate to 4 monkeys, both salivary and serum testosterone levels increased promptly and in parallel. The salivary testosterone levels correlated well with the serum testosterone values. The study suggests that, as in the human, determination of salivary testosterone can be used as an index of free testosterone in this animal. Moreover, the monkey can be used as a model for studies in the human involving monitoring of salivary testosterone.

Suppression of pituitary and testicular function in normal men by constant gonadotropin-releasing hormone agonist infusion.

In a trial for male fertility control the effects of constant GnRH agonist (buserelin) infusion on pituitary and testicular function was investigated. The agonist was administered sc for 12 weeks to two groups of normal young men using extracorporeal osmotic minipumps. Seven men received 118 +/- 24 (SD) micrograms/day from pumps changed biweekly and four men received 230 +/- 27 micrograms/day from pumps changed weekly. After an initial rise serum LH, FSH, and testosterone decreased. The decrease occurred faster in the high dose group and these subjects had no LH response to acute GnRH stimulation after 4 weeks of treatment, whereas the response was drastically reduced in the group receiving the low dose. Androgen substitution with testosterone undecanoate (80-120 mg orally daily) was initiated when the subjects complained of decreased libido and/or potency or when serum testosterone fell below 10 nmol/liter on average in the fifth week. Sperm counts decreased significantly and below the lower normal limit of 20,000,000/ml. The nadir was reached in week 12 of treatment in the high dose group, and in week 4 post treatment in the low dose group. Despite desensitization of the pituitary and impaired testicular function azoospermia did not occur. A higher dose of agonist appears to be required to achieve this goal.

Testosterone supplementation attenuates the antifertility effects of an LHRH agonist in male rhesus monkeys.

Continuous administration of LHRH agonists in high doses disrupts pituitary and testicular function, thus providing an approach to male fertility control. However, testosterone supplementation is required to prevent the side effects associated with low androgen concentrations resulting from chronic LHRH agonist treatment. Three adult male rhesus monkeys were treated with the LHRH agonist, Buserelin, using osmotic minipumps implanted subcutaneously. Testosterone was administered simultaneously via Silastic capsules. This combined treatment led to a marked decrease in testicular volume, and all animals were oligospermic within 8-15 weeks of treatment. Azoospermia was, however, not achieved even after 22 weeks of treatment although in a previous study in which the LHRH agonist had been administered alone, azoospermia had been achieved after 8-10 weeks. It is concluded that in this primate species testosterone supplementation attenuates the suppressive effects of LHRH agonist infusion on spermatogenesis.

Reversible induction of azoospermia in rhesus monkeys by constant infusion of a gonadotropin-releasing hormone agonist using osmotic minipumps.

This study documents the long term, reversible, antireproductive effects of GnRH agonist treatment in adult male rhesus monkeys. Constant sc infusion of the GnRH agonist buserelin by osmotic minipumps over 20 weeks resulted in an initial rise in serum LH, followed by a decline to undetectable levels, indicating pituitary desensitization. This rise and fall of plasma LH was paralleled by serum testosterone concentrations. The RHLH response to an iv bolus injection of GnRH was completely abolished, and the corresponding Leydig cell response was also lost. Testicular volumes decreased markedly, and spermatogenesis was inhibited to azoospermic levels. Spontaneous and electrostimulated ejaculatory activities were lost under prolonged buserelin infusion. The animals were then supplemented with exogenous testosterone to reestablish ejaculatory behavior which had been curtailed under low circulating androgen levels, and azoospermia persisted. Such pronounced effects could not be demonstrated in our previous studies using daily or twice daily injections with higher agonist doses. When treatment was stopped after 20 weeks, the inhibitory effects of the GnRH agonist were reversible, and full pituitary and gonadal functions were recovered. It is concluded that constant infusion of GnRH agonist is far more effective in male rhesus monkeys than daily injections and that the suppressive effects of GnRH agonist application are fully reversible. Thus, a suitable primate model for further research on a GnRH agonist-based male contraceptive has been established.

Pituitary and testicular functions in sexually mature rhesus monkeys under high-dose LRH-agonist treatment.

Treatment with high doses of LRH-agonists leads to a down-regulation of testicular LH/hCG receptors and is accompanied by a suppression of spermatogenesis in some laboratory animals. In order to test whether this may provide an approach to male fertility control, 4 adult rhesus monkeys were treated with very high doses of LRH-agonist, D-Ser(TBu)6-LHR-ethylamide (100 micrograms daily) for 10 weeks during the breeding season. There was a decrease in testicular volume after 3 weeks of treatment. Serum LH and testosterone levels were suppressed. Sperm counts were stimulated during the first 6 weeks of treatment. At the end of treatment sperm counts, although lower, were still in the normal range. The chronic treatment schedule resulted in a decrease in pituitary responsiveness to an acute challenge with 4 micrograms agonist iv, indicating a desensitization of the pituitary. However, the testosterone response remained unchanged. This study using extremely high doses of the agonist indicates that, compared to the rat, male primates are far more resistant to the suppressive effects of LRH-agonists.

Effects of gonadotrophin treatment in vivo on testicular function in immature rhesus monkeys (Macaca mulatta).

Changes in testicular histology and concentrations of testosterone and oestradiol 17 beta in testicular tissue and plasma have been studied following administration of gonadotrophins (oFSH, oLH, hCG and PMSG) to immature male monkeys. Treatment with FSH (1 mg/day) or PMSG (100 IU/day) for five days, induced a marked enlargement of the seminiferous tubules and increase in the Sertoli cell cytoplasm. Injections of LH (1 mg/daily) or hCG (100 IU/daily) administered similarly, failed to produce hypertrophy of the Sertoli cell. In LH, hCG and PMSG stimulated testes morphologically differentiated interstitial cells could be recognized. FSH did not produce any detectable effect on the intertubular tissue. A significant increase in testicular and plasma testosterone levels was observed with LH, hCG and PMSG. FSH was shown to be much less effective in stimulating androgenesis. An increase in testicular oestradiol production over that of controls, was observed in FSH and PMSG treated monkeys but not in animals treated with LH or hCG.