The effects of short-term oral phytoestrogen supplementation on the hypothalamic-pituitary-testicular axis in prostate cancer patients

Background Here we evaluate the effects of oral phytoestrogen supplementation on hypothalamic‐pituitary‐testicular (HPT) axis in CaP patients. Methods We recruited 40 men about to undergo radical prostatectomy for CaP to receive either 240 mg of clover phytoestrogens or placebo daily for 2 weeks. Serum hormone levels were measured before and after treatment. In addition, recombinant cell bioassay was used to measure serum androgen bioactivity (ABA). Results Phytoestrogen treatment increased serum LH from mean of 3.4–5.2 IU, P = 0.03. Concomitantly, non‐significant trend towards decline in serum T, cfT and ABA values was noted. However, mean serum LH/T ratio was upregulated from 0.20 to 0.48 IU/nM, P = 0.004, suggesting compensated hypogonadism. During the course of treatment, serum concentration of equol correlated strongly with the concomitant decrease in ABA (r = −0.586, P = 0.022). Conclusions Phytoestrogen treatment interferes with HPT axis in CaP patients by inducing testicular resistance to LH and compensated hypogonadism. Prostate 66: 1086‐1091, 2006. © 2006 Wiley‐Liss, Inc.