Ontogeny of 3[β‐Hydroxysteroid Dehydrogenase/Δ5–Δ4 Isomerase (3β‐HSD) in Human Testis as Studied by Immunocytochemistry

Abstract

ABSTRACT: The enzyme complex 3β‐hydroxy‐5‐ene‐steroid dehydrogenase/Δ5–Δ4 isomerase (3β‐HSD) is involved in the biosynthesis of all classes of active steroids, including androgens. To correlate possible changes in 3β‐HSD with the well‐known variations in testosterone secretion during development, the authors localized this enzyme by immunocytochemistry during fetal and postnatal periods of development in the human testis. In the fetal testis, 3β‐HSD was detected in Leydig cells during the second and third trimester of gestation. In 8‐month‐old and 11‐year‐old boys, however, no immunoreaction could be detected in the testis. In pubertal boys, Leydig cells appeared well developed and immunopositive. Since the fluctuations in 3β‐HSD immunoreactivity are similar to those already observed for androgen secretion, activation of 3β‐HSD by trophic hormones may play an important role in androgen production during fetal and postnatal development.