Stronger suppression of serum testosterone and FSH levels by a synthetic estrogen than by castration or an LH-RH agonist

Abstract

Serum levels of LH, FSH and testosterone (T) were measured by radioimmunoassays in 36 patients with advanced prostate cancer before and during androgen ablation therapies. Both leuprolide acetate (LH-RH agonist: LHRH-A) and diethylstilbestrol diphosphate (DES-DP) administration decreased serum LH significantly to an undetectable level (LHRH-A: P<0.01, DES-DP: P<0.05). LHRH-A and DES-DP diminished serum FSH to 20% of the pre-treatment level (P<0.005) and to an undetectable level (P<0.001), respectively. LHRH-A and DES-DP decreased serum T to the castration level and an undetectable level, respectively (P<0.001). Serum levels of the same 3 hormones before and after DES-DP administration were measured in 8 patients who received DES-DP after LHRH-A treatment or castration because of relapse of the disease. DES- DP lowered serum FSH further than LHRH-A to an undetectable level (P<0.005) and diminished T further than previous treatments to an undetectable level (P<0.05 vs. LHRH-A, P<0.01 vs. castration). These results suggest that 1) DES-DP is able to reduce T production from extra-testicular site(s), and achieve the minimal serum T level, and 2) this DES-DP action appears to be one of the mechanisms of the effectiveness of estrogen on refractory prostate cancer after castration or LHRH-A. In addition, basal (independent of LH-RH) FSH secretion in elderly men is about 20% of total FSH secretion and DES-DP inhibits the basal FSH secretion at the level of the pituitary.