Inhibin is a hormone which may be used in the evaluation for testicular function.   Inhibin B is a hormone secreted by the Sertoli cells.  It has been shown that lower levels of Inhibin B and even loss of levels of Inhibin B occur in men after chemotherapy or radiation therapy.[6]  Others have suggested that using reference values for Inhibin B and Inhibin B to FSH ratio are more sensitive markers of male infertility than FSH alone [7].  Even so, Inhibin B as a direct marker determining spermatogenesis has shown conflicting results in the literature, and does not seem to predict sperm presence in azoospermic patients[8].  Because of the conflicting results in the literature, the potential role of serum Inhibin B as a marker for predicting spermatogenesis is not routinely used.