Partial 3 beta-hydroxysteroid dehydrogenase deficiency presenting as new-onset gynecomastia in a eugonadal adult male.

The postpubertal clinical presentation of 3 beta-hydroxysteroid dehydrogenase deficiency (3B-HSD deficiency) is less well-defined for adult males than for adult females, who often present with hirsutism. We describe a male with normal puberty who presented with new-onset gynecomastia at age 24. Common causes of gynecomastia were excluded. Dehydroepiandrosterone-sulfate (DHEA-S), estradiol, estrone, and 24-hour urinary 17-ketosteroid levels were elevated. A feminizing tumor was considered; biochemical tumor markers, chest x-ray, ultrasound of testes, and abdominal computed tomography (CT) scan were negative. Dexamethasone-suppression testing showed normal suppression of 24-hour urinary adrenal steroids. Cosyntropin-stimulation testing showed normal cortisol, 11-deoxycortisol, 17-OH progesterone (17-OHP), and aldosterone levels, but significant elevations of pregnenolone (preg), 17-OH preg, progesterone, DHEA, and androstenedione (A) levels. The sperm count was high and gonadotropin-releasing hormone (GnRH)-stimulation testing showed a normal increase in testosterone (T) level, suggesting that the defect did not involve the testes. It is concluded that this patient's gynecomastia is due to 3B-HSD deficiency with an associated alteration in sex hormone ratios. To our knowledge, this is the first well-described adult male with normal gonadal function presenting with postpubertal gynecomastia due to 3B-HSD deficiency. This defect may be a frequently unrecognized cause of gynecomastia.