Males with classical 3β-hydroxysteroid dehydrogenase (3β-HSD) deficiency manifest appropriate secondary sexual maturation with an elevation in serum testosterone levels at pubertal age. To define the origin of serum testosterone, we evaluated a male patient with classical 3β-HSD who showed pubertal development. High values of testosterone and a ratio of Δ5 to Δ4 steroids in the spermatic vein indicated direct production of considerable amounts of testosterone and a persistent defect of 3β-HSD activity in the gonad. Immunohistochemical analysis showed distinct immunoreactivity in the Leydig cells of the patient. The patient was homozygous for a nonsense mutation in the type-II 3β-HSD gene. We propose that gonadal type-I 3β-HSD could be expressed by gonadotropin stimulation at pubertal age, and Δ4-steroid precursors would convert to testosterone.
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