Bioactive and peripheral androgens in prepubertal simple hypertrichosis

Prepubertal simple hypertrichosis is characterized by excessive growth of vellus hair in children without other signs of endocrinopathies. The aetiology is unknown and it is not clear if it is an abnormal entity or an extreme form of the normal range of hair growth. Sixteen girls (aged 7 +/- 1.9 years, mean +/- SD) with prepubertal simple hypertrichosis and, as controls, 12 normal age-matched girls were studied. All patients were in preadrenarchal age and in all patients an ACTH test was performed to exclude non-classical forms of congenital adrenal hyperplasia. Testosterone (T), androstenedione (A), dehydroepiandrosterone sulphate (DHA-S), dihydrotesterone (DHT), 3 alpha-androstanediol (3Ad) and its glucuronide (3AG), and sex hormone binding globulin (SHBG) were evaluated and free testosterone (FT) and T/SHBG ratio were calculated in all subjects. In all patients we found T, A and DHA-S plasma levels comparable to controls, excluding an increased glandular androgen secretion. No significant differences, compared to controls, were observed for SHBG, FT and T/SHBG ratio, suggesting a normal T bioavailability. DHT plasma levels were significantly increased with respect to controls (0.42 +/- 0.04 vs 0.11 +/- 0.03 nmol/l; P less than 0.002) whereas 3Ad and 3AG were comparable to controls. The very significant increase in DHT plasma levels, without a parallel increase in 3Ad and 3AG found in our cases with prepubertal simple hypertrichosis, is difficult to explain. The clinical and biochemical significance of the high DHT plasma values needs more investigation.