Further in vitro steroid metabolic studies of testicular 17beta-reduction deficiency

17beta-Hydroxysteroid dehydrogenase 3 deficiency

Five known isoenzymes catalyze the 17beta-hydroxysteroid dehydrogenase reaction that controls the interconversion of estrone and estradiol and of testosterone and androstenedione. Mutations in the 17beta-hydroxysteroid dehydrogenase 3 gene impair the formation of testosterone in the fetal testis and give rise to genetic males with normal male Wolffian duct structures but female external genitalia. Such individuals are usually raised as females but virilize at the time of puberty as the result of a rise in serum testosterone. The 14 mutations characterized to date in 17 affected families include 10 missense mutations, 3 splice junction abnormalities, and 1 frame shift mutation. Three of the mutations have occurred in more than 1 family. The usual mechanism for testosterone formation in affected individuals at puberty appears to be conversion of androstenedione to testosterone in extraglandular tissues by one or more of the unaffected 17beta-hydroxysteroid dehydrogenase isoenzymes.

Hirsutism, polycystic ovarian disease, and ovarian 17-ketosteroid reductase deficiency

We studied an 18-year-old woman with progressive hirsutism, secondary amenorrhea, and polycystic ovarian disease. Excess androstenedione was secreted by the ovaries, most likely because of a genetic deficiency of ovarian 17-ketosteroid reductase, the enzyme that converts androstenedione to testosterone. Markedly elevated basal plasma levels of androstenedione, estrone, and testosterone were regulated by gonadotropin but not by ACTH. The rate of androstenedione production in the patient's blood at base line and after administration of dexamethasone was very high (10.0 to 11.6 mg per day; value in control women with hirsutism, less than 4.1 mg per day), whereas her blood production of testosterone was 0.64 to 0.7 mg per day, similar to or higher than that in control women with hirsutism. The fractional blood conversion ratio of androstenedione to testosterone was normal (5.6 percent). Thus, 88 to 93 percent of the testosterone in the blood was derived from the peripheral conversion of androstenedione, and very little testosterone was secreted by the ovaries. These in vivo biochemical data suggest that the patient had a deficiency of ovarian 17-ketosteroid reductase activity but normal pubertal activity. The patient's two younger sisters with peripubertal symptoms of androgen excess also had elevated serum levels of androstenedione. We propose that the increased secretion of androstenedione in the three siblings in this family was probably due to a genetic deficiency of ovarian 17-ketosteroid reductase.

Incomplete masculinization due to a deficiency of 17 beta-hydroxysteroid dehydrogenase: comparison of prepubertal and peripubertal siblings

Incomplete masculinization due to a deficiency of 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) was investigated in siblings aged 4 years (Case 1) and 12 years (Case 2). Diagnosis was based on increased ratios of androstenedione (A) to testosterone (T) in blood, and impaired reduction of A to T by 17 beta-HSD in vitro in the testes. Impairment was total in Case 2 but partial in Case 1. Case 2 also showed deficient conversion of dehydroepiandrosterone (DHA) to androstenediol and of oestrone to oestradiol by 17 beta-HSD which were normal in Case 1. Oxidation of T to A by 17 beta-HSD and conversion of 17 alpha-hydroxyprogesterone to A by 17,20 desmolase were normal in the testes of both siblings. 3 beta-HSD conversion of DHA to A was normal in Case 1, but markedly increased in Case 2. In contrast to testicular findings, 17 beta-HSD reduction of A to T in genital skin fibroblasts from Case 2 was normal and diagnosis would not have been possible from studies of measurements of this enzyme in skin. The severity of the testicular 17 beta-HSD deficiency in the peripubertal compared with the prepubertal sibling suggests either considerable intra-familial variation in the extent of the enzyme defect or that puberty may aggravate this disorder. The normal reductive action of 17 beta-HSD in skin, despite impaired action in testes, suggests involvement of more than one iso-enzyme.