Familial incomplete virilization due to partial end organ insensitivity to androgens.

A 16-yr-old 46 XY individual with a familial incomplete male pseudohermaphroditism closely resembling the syndrome described by Gilbert-Dreyfus et al. was studied. The patient's habitus was masculine despite the presence of a small phallus, pseudo-vaginal perineal hypospadias, bifid scrotum, gynecomastia, and diminished virilization. Blood samples obtained at 20-min intervals were submitted to hormone analysis. Episodic fluctuations of plasma gonadotropins with mean values of LH above the normal male range and FSH within normal limits were observed. Moderately elevated plasma testosterone and increased plasma estradiol also showed episodic oscillations. The administration of LH-releasing hormone resulted in a significative increase of plasma LH and FSH. Testicular biopsy revealed the presence of seminiferous tubules with few spermatogonia and no spermatocytes, and normal sertoli and interstitial cells. Gonadal stimulation with hCG for 4 consecutive days induced a significative increase of plasma testosterone and estradiol. The daily administration of 50 mg of testosterone propionate for 3 days neither depressed the circulating levels of gonadotropins nor modified the pulsatile pattern of gonadotropins release. Administration of testosterone and 5alpha-dihydrotestosterone propionate failed to diminish plasma LH and FSH levels. Testosterone administration for 10 weeks also failed to induce virilization. These results are similar to those observed in patients with testicular feminization syndrome, and the underlying abnormality involves a partial defect of the mechanism of action of testosterone rather than decreased androgen biosynthesis. According to a recently proposed classification this individual corresponds to the type 1 incomplete male pseudohermaphroditism.