Increased serum inhibin B levels after varicocele treatment.

Inhibin B is secreted by Sertoli cells in response to FSH and is the major feedback regulator of FSH secretion in man. The serum inhibin B level has emerged as a good marker of spermatogenesis and Sertoli cell function. Varicocele has been associated with infertility and disturbed spermatogenesis. We have studied the effect of varicocele treatment on serum inhibin B levels, with the aim of investigating the effect on spermatogenesis and the involvement of the Sertoli cell in varicocele pathophysiology. In a pre-post test design, the effect of varicocele surgery on inhibin B levels was studied in 30 infertile men. Endocrinology (inhibin B, FSH, LH, SHBG and testosterone) and semen analysis (sperm concentration, motility and morphology). In men receiving varicocele treatment, a significant increase in serum inhibin B levels was observed from 133.9 +/- 13.4 pretreatment to 167.8 +/- 16.1 ng/l after treatment (mean +/- SEM, P < 0.0001). No significant changes were observed in serum levels of FSH, LH and testosterone. The serum SHBG level decreased from 32.9 +/- 3.5 to 28.6 +/- 3.4 nmol/l (mean +/- SEM, P = 0.04) and the free androgen index was significantly increased from 66 +/- 5.9 pretreatment to 85 +/- 6.8 after treatment (P = 0.02, mean +/- SEM). Semen analysis showed a significant improvement in sperm concentration, from 6.5 +/- 1.9 pretreatment to 19.3 +/- 4.9 x 106/ml after treatment (P = 0.003, mean +/- SEM), and in sperm motility from the baseline level of 17 +/- 3 to 32 +/- 4% after treatment (P = 0.001, mean +/- SEM). Varicocele treatment can increase serum inhibin B levels, indicating improvement of spermatogenesis and Sertoli cell function. This finding suggests that the pathophysiology of varicocele involves impairment of Sertoli cell function or a different distribution of germ cell stages.