Graded testosterone infusions distinguish gonadotropin negative- feedback responsiveness in asian and white men - A clinical research center study

Recently, multicenter clinical trials to determine male contraceptive efficacy disclosed that testosterone-induced suppression of spermatogenesis to azoospermia occurred in about 90% of Asian but only 60–70% of white men. To test whether there are ethnic differences in the sensitivity of gonadotropin secretion to suppression by testosterone, we administered constant infusions of testosterone at 0, 7, 14, and 28 mg/1.7 m2·24 h iv for 48 h to 9 Asian and 8 white normal male volunteers (22–42 yr old). During the last 8 h of each infusion dose, 10-min frequent blood sampling was carried out for later LH and FSH measurements by sensitive fluoroimmunoassays. Analyses of LH secretory pulses showed that LH pulse width, height, area, and total area under the curve (LH concentration vs. time) were significantly more suppressed in Asians than in whites during the lowest infusion dose of testosterone. With increasing testosterone dose, the suppression of pulsatile LH secretion was not different in the two ethnic grou...