SERUM INHIBIN-B AS A MARKER OF SPERMATOGENESIS

Inhibin B is produced by Sertoli cells, provides negative feedback on FSH secretion, and may prove to be an important marker for the functio ning of seminiferous tubules. The purpose of the present study was to examine the relationship between the spermatogenic function of the tes tis of subfertile men and the plasma concentrations of inhibin B and F SH. These parameters were estimated in a group of 218 subfertile men. Serum inhibin B levels were closely correlated with the serum FSH leve ls (r = -0.78, P < 0.001), confirming the role of inhibin B as feedbac k signal for FSH production. The spermatogenic function of the testis was evaluated by determining testicular volume and total sperm count. Inhibin B levels were significantly correlated with the total sperm co unt and testicular volume (r = 0.54 and r = 0.63, respectively; P < 0. 001). Testicular biopsies were obtained in 22 of these men. Inhibin B was significantly correlated with the biopsy score (r = 0.76, P < 0.00 1). Receiver operating characteristic analysis revealed a diagnostic a ccuracy of 95% for differentiating competent from impaired spermatogen esis for inhibin B, whereas for FSH, a value of 80% was found. We conc lude that inhibin B is the best available endocrine marker of spermato genesis in subfertile men.