Effects of pharmacological doses of testosterone and dihydrotestosterone on the hypothalamic-pituitary axis function of Klinefelter patients.

Six patients affected by Klinefelter's syndrome (KS) were treated with testosterone propionate (TP) 100 mg im daily for 4 days and one month later the same patients received dihydrotestosterone propionate (DHTP) 100 mg im daily for 4 days. Plasma levels of LH, FSH, PRL, testosterone (T) and dihydrotestosterone (DHT) have been measured in these patients for 8 days during and after TP and DHTP treatment. TP administration reduced LH levels only transiently, while a more prolonged reduction was observed for FSH. DHTP administration produced a late and transient reduction of LH and a very late reduction of FSH. PRL levels increased significantly during and after TP administration. Our data suggest that in Klinefelter patients: i) DHT is less effective than T in suppressing gonadotropin concentrations, ii) the increased PRL levels observed during and after TP administration are not due to a pure androgenic effect, but are probably related to an increased conversion rate of T to estradiol.