Effect of long-term, high-dose estrogen treatment on prolactin levels: a retrospective analysis.

BACKGROUND: Exogenous estrogen administration causes prolactinoma formation in rats and there are anecdotal reports of estrogen treatment and prolactinoma formation in human transsexuals with male-to-female gender reassignment. It remains unclear whether chronic exposure to high-dose estrogen in women is linked with hyperprolactinemia. Aim The aim of this study was to determine whether high-dose, long-term subcutaneous estrogen treatment affected prolactin and gonadotropin levels.

DESIGN: This was a retrospective, observational and descriptive analysis of 101 women treated for up to 15 years following a combined hysterectomy and oophorectomy.

METHOD: A total of 101 women who were receiving estradiol implants 50-100 mg 4-6 monthly, on demand for 5-15 years following abdominal hysterectomy and bilateral salphingo-oophorectomy were studied. The main outcome measures were levels of serum prolactin, follicle stimulating hormone (FSH) and luteinizing hormone (LH). Results The 101 patients received an average cumulative estrogen dose of (mean +/- SEM) 1239 +/- 12 mg per person, 18.96 +/- 1.2 mg/kg body weight, over a period of 5-15 years. The trough estradiol levels after withholding implants for 6 months were high (1047.9 +/- 52 pmol/l). Their average prolactin level of 88.88 +/- 9.2 mU/l was normal and their FSH (1.96 +/- 0.42 IU/l) and LH (2.97 +/- 0.88 IU/l) levels were relatively suppressed.

CONCLUSION: These data are reassuring that, even in women exposed to very high doses of estrogen for a prolonged period of time, hyperprolactinemia is unlikely to occur.