Relationship of inhibin serum level to bioactive and immunoreactive FSH in oligospermic and azoospermic patients

Summary. The purpose of the study described here was to evaluate the relationship between inhibin (INH) and bioactive FSH (B-FSH) or immunoreactive FSH (I-FSH) in oligoazoospermic patients. To accomplish this, the authors measured serum levels of INH, I-FSH, B-FSH, LH and testosterone (T) in 98 male patients attending the Andrology Centre at Malphighi Hospital (Bologna) for infertility workup. On the basis of the mean sperm concentration, patients with sperm output ≥4 × 10⁷ ml^?1 (n = 30) formed the control group (group A), whereas oligozoospermic patients were divided arbitrarily into three groups. Sperm concentrations for these groups ranged as follows: B, 2–4×10⁷ml^?1 (n = 14); C, 5× 10⁶-2× 10⁷ml^?1 (n = 18); D, < 5 × 10⁶ ml^?1 (n = 17). In addition, the authors studied a group of patients with possible nonobstructive azoospermia (n = 19, group E), confirmed in 16 of them through testicular biopsy. There were no significant differences in serum levels of LH and T among groups. However, azoospermic patients had a significant reduction of the T/LH ratio. Similarly, B-FSH and B/I-FSH ratios were significantly elevated only in group E. INH serum levels did not show any appreciable changes among groups and in azoospermic patients INH correlated significantly and in a positive manner with I-FSH serum levels and negatively with B/I-FSH and T/LH ratios. Within the azoospermic patient group no consistent relationship was evident between INH serum concentration and various degrees of spermatogenetic arrest. Indeed, patients having the same qualitative tubular damage, presented low, normal or high INH levels in serum. The failure of serum INH to correlate with the degree of tubular damage may be due either to the fact that the damage to Sertoli cells in azoospermia is not severe enough to decrease cell function, or to the lack of a specific assay for measuring INH.