XVII Harry Benjamin International Gender Dysphoria Association Symposium
31 October - 4 November 2001, Galveston, Texas, U.S.A.

Effects of Androgen Treatment and of Androgen-Derived Estrogens on Prolactin (PRL) Levels in a Female-to-Male Transsexual with a Prolactinoma

TOORIANS, A.W.F.T. The Netherlands
Co-author: L.J.G. Gooren (The Netherlands)

Human pituitary adenomas and normal pituitary glands express receptors for both androgens and estrogens. An earlier report documented that testosterone (T) administration increased PRL levels and tumor size of a prolactinoma. (1) It was hypothesized that (part of) this effect might be ascribed to T-derived estrogens. We present a case report, which indeed confirms contribution of T-derived estrogens to PRL levels in a subject with a prolactinoma. Our patient was a 22 year old female-to-male transsexual with menstrual disturbances due to a microprolactinoma. Initial PRL level was 5.4 U/l (N<0.7), T: 1.4nmol/l (N <2.5), E2: <90pmol/l (N>90). Upon three months administration of parenteral T (SustanonR 250mg i.m./2 weeks) PRL rose to 7.6 U/l. T was 17nmol and E2: <90pmol/l) did not result in a fall of PRL level (7.9U/l). Bromocriptine 5 mg/day reduced PRL to 1.4-3.5 U/l. When a lower dose of T (100mg SustanonR/2 weeks) was administered, while bromocriptine 5 mg/day was continued, PRL increased to 4.9-6.6 U/l. The patient tolerated various dopamine agonists poorly and they were withdrawn. T was continued but now combined with the estrogen-receptor-antagonist tamoxifen 20mg/day whereupon PRL fell to 1.9 U/l.

Conclusions: 1) androgens are capable of increasing PRL values even when dopamine agonists are given. 2) In view of the PRL lowering effects of the estrogen receptor antagonist tamoxifen part of this effect is to be ascribed to androgen-derived estrogens.

1. Prior et al. J. Clini Endrocrinol Metab 1987; 64:39 1-4.