Serum inhibin B levels during male childhood and puberty

Inhibin B is a testicular peptide hormone that regulates FSH secretion in a negative feedback loop. In mates serum levels of inhibin B are detectable throughout life with prominent changes in the first year of life and during puberty. Serum inhibin B is normally detectable throughout childhood where it is a direct marker of the presence and function of Sertoli cells. The i nhibin B analysis has proven useful in the diagnosis of patients with non-p alpable testes. Undetectable or low inhibin B levels are observed in boys w ith either congenital or acquired absence of testicular tissue whereas norm al or near-normal levels are seen in cryptorchidism and disorders with pres erved Sertoli cell function in spite of absence of germ cells or impaired a ndrogen biosynthesis or action. During puberty a developmental change in th e regulation of serum inhibin B occurs. In contrast to childhood inhibin B levels, inhibin B production in adult men is dependent on the presence of c ertain germ cells in the seminiferous tubules, most likely involving the pa chytene spermatocytes and early spermatids. Thus, in adult men serum inhibi n B levels are closely related to spermatogenesis with undetectable or low levels observed in SCO syndrome and early stage spermatogenic arrest wherea s normal or near normal levels are observed in men with late stage spermato genic arrest or obstructive forms of azoospermia. These clinical findings a re in accordance with immuno-histological studies of the expression of inhi bin B subunits in human testis. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.