Effects of Sex Steroids on the Positive Estrogen Feedback Mechanism in Intact Women and Castrate Men

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Abstract
We studied the effects of prolonged testosterone treatment on ovulatory function and positive estrogen feedbackin women and of prolonged estrogen priming on gonadotropinfeedback in castrate men. An estrogen provocation test wascarried out in 4 groups of transsexual subjects: 12 female transsexualsin their early follicular phase (days 3–5; group 1A), 8females who had been treated with Depo-testosterone (T) for 3–6 months (group IB), 11 men who had been castrated 3 monthspreviously (group 2A), and 4 male castrates treated with oralestrogen for 3 months starting 3 months after castration (group2B). The estrogen provocation test consisted of 3 GnRH tests(100 μg) carried out immediately before (0 h) and 44 and 92 hafter an im injection of estradiol valerate (10 mg). Responses tothe estrogen provocation test in women with normal menstrualcycles (group 1A) were typically female. After initial suppressionat 44 h, a LH surge (positive feedback) occurred at 92 h. Pituitary responsiveness, however, was amplified both at 44 and 92 h.Prolonged T priming of women in group IB did not inhibit theestrogen-induced LH surge, nor was the amplitude of the surgeblunted. Removal of androgens and other testicular factors(group 2A) did not result in the appearance of an estrogeninducedLH surge. On the other hand, prolonged estrogen primingin male castrates (group 2B) resulted in activation of thepositive feedback mechanism; a LH surge in response to theestrogen provocation occurred. The results of the present studyimply that 1) contrary to an earlier suggestion, testosterone doesnot block or blunt the LH surge, indicating that it is probablynot responsible for suppressing the LH surge in normal men; 2)testosterone can cause ovulatory failure without suppressing theLH surge in women; and 3) prolonged estrogen priming may beinvolved in activation of the positive feedback mechanism inhumans.

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