No male hormonal contraceptive is ready for clinical use. Most trials were small exploratory studies. Their power to detect important differences was limited and their results imprecise. In addition, assessment of azoospermia can vary by sensitivity of the method used. Future trials need more attention to the methodological requirements for RCTs. More trials with adequate power would also be helpful.
Effects of chronic testosterone administration in normal men: safety and efficacy of high dosage testosterone and parallel dose-dependent suppression of luteinizing hormone, follicle-stimulating hormone, and sperm production.
In normal men, chronic testosterone (T) administration results in negative feedback suppression of gonadotropin and sperm production. However, azoospermia is achieved in only 50-70% of men treated with high dosages of T. Furthermore, the relative sensitivity of LH and FSH secretion to chronic administration of more physiological dosages of T is unclear. We determined whether a T dosage higher than those previously given would be more or less effective in suppressing spermatogenesis and whether, within the physiological range, T would exert a more selective effect on LH than on FSH secretion. After a 4- to 6-month control period, 51 normal men were randomly assigned to treatment groups (n = 9-12/group) receiving either sesame oil (1 mL) or T enanthate (25, 50, 100, or 300 mg, im) weekly for 6 months. Monthly LH and FSH levels by RIA and twice monthly sperm counts were determined. During treatment, T levels were measured daily between two weekly injections. Chronic T administration in physiological to moderately supraphysiological dosages resulted in parallel dose-dependent suppression of LH, FSH, and sperm production. T enanthate (50 mg/week) suppressed LH and FSH levels and sperm counts to 50% of those in placebo-treated men (ED50). T enanthate (300 mg/week), was no more effective than 100 mg/week in suppressing LH, FSH, and sperm production. Serum T levels in men who received 100 and 300 mg/week T enanthate were 1.5- and 3-fold higher than those in placebo-treated men, respectively. Except for mild truncal acne, weight gain, and increases in hematocrit, we detected no significant adverse health effects of chronic high dosage T administration. We conclude that 1) LH and FSH secretion are equally sensitive to the long term negative feedback effects of T administration; 2) sperm production is suppressed in parallel with the LH and FSH reductions induced by chronic T administration; and 3) even at the clearly supraphysiological dosage of 300 mg/week, T enanthate does not reliably induce azoospermia in normal men. However, there was also no evidence of a stimulatory effect of this T dosage on spermatogenesis. Furthermore, we found no evidence of major adverse health effects of T administered chronically even at the highest dosage.