Rapid endocrine effects of tamoxifen and testolactone in prostatic carcinoma patients

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Abstract
The short‐term (6‐day) endocrine effects of tamoxifen and testolactone were investigated in men with prostatic carcinoma. Tamoxifen treatment (20 mg/day) did not affect the gonado‐tropin levels, but it temporarily increased prolactin, induced sex hormone‐binding globulin production, and suppressed peripheral serum progesterone, 17‐hydroxyprogesterone, an‐drostenedione, testosterone, and 5α‐dihydrotestosterone concentrations. These changes were attributed to the estrogenic properties of tamoxifen, since no changes in peripheral serum estradiol concentrations were observed. Testolactone (1000 mg/day) decreased peripheral estradiol concentrations by 50% and increased the concentrations of the neutral steroids measured. The increases in serum FSH and LH were very small. This study corroborates the early estrogen‐like action of tamoxifen, and the experiment with testolactone further suggests that endogenous estradiol has physiological functions in man, regulating gonadotropin and androgen production.