Lack of correlation between sex hormone binding globulin and free testosterone in some cases of "idiopathic" hirsutism.

Plasma 3 alpha-androstanediol levels are increased in a high percentage of hirsute women, including those with normal plasma levels of its precursors, repeatedly evaluated during the menstrual cycle. To better ascertain the origin of this form of hirsutism, so called "idiopathic", 17 hirsute women (aged 19.5 +/- 4.8 SD yr), with normal bw, showing an isolated increase in plasma 3 alpha-androstanediol (0.65 +/- 0.18 SD nmol/l) were studied in basal conditions (on day 6, 7, 17, 18 of the menstrual cycle). A hirsute female (aged 14 yr) with congenital adrenal hyperplasia due to 21-hydroxylase deficiency was also included in the protocol. Sex hormone binding globulin was evaluated using a saturation method (dihydrotestosterone- 3H 0.5-25 nM) with and without 200x cold dihydrotestosterone. Maximum number of binding sites and Ka were calculated in all cases with Scatchard analysis. Free testosterone was evaluated by the equilibrium dialysis technique. The results obtained showed a significant increase in Ka values in 10 out of the 17 cases; low plasma levels of sex hormone binding globulin in 13 cases and normal levels in 4 cases; high levels of free testosterone fraction in 5 cases and in the upper limits of the normal range or normal in the remaining 12. These findings demonstrate that some cases of "idiopathic" hirsutism may present an alteration in the binding affinity of the sex hormone binding globulin which may be genetically transmitted, being found to be increased in two sisters and in their brother.