Inhibin B plasma concentrations in infertile patients with DAZ gene deletions treated with FSH.

Objective: The DAZ (deleted in azoospermia) gene family on the Y chromosome long arm is the major candidate for the AZFc (azoospermia factor c) phenotype of male infertility and it is expressed only in germ cells. The aim of the study was to assess Sertoli cell function in subjects with AZFc deletions.

Design: Case-control, prospective study.

Methods: We have studied six severely oligozoospermic subjects with AZFc-DAZ deletions, and looked whether they responded in terms of inhibin B production to a 1 month FSH treatment. These patients were compared with three groups of patients affected by different spermatogenic alterations not related to deletions on the Y chromosome.

Results: Although affected by severe testiculopathy, patients with AZFc-DAZ deletions had only slightly elevated FSH, and normal inhibin B plasma concentrations. Inhibin B responded normally during FSH treatment, supporting the hypothesis that Sertoli cells are not altered. On the contrary, other severe testiculopathies not related to Y chromosome deletions showed high FSH and low inhibin B concentrations, with no response to FSH treatment. In these cases the cause of the spermatogenic defect probably damaged both germ and Sertoli cells. Finally, idiopathic patients with a hormonal status similar to Y-deleted patients (slightly elevated FSH and normal inhibin B concentrations) did not respond to FSH treatment, suggesting that Sertoli cells were already at their maximal functional capability.

Conclusions: These data confirm that Sertoli cell function is not damaged in patients with AZFc-DAZ deletions and that the strong reduction of germ cells does not affect the FSH-inhibin B feedback loop.