Serum testosterone fractions in women: normal and abnormal clinical states

The potential usefulness of determining serum testosterone (T) fractions in women, ie, sex hormone-binding globulin (SHBG)-bound T, albumin-bound T (Alb-T), and free T (FT) fractions, was explored in a variety of clinical situations. Serum T, SHBG, and albumin concentrations were measured by standardized methods and using binding constants of T to SHBG and albumin, we calculated serum T fractions, which agreed remarkably with measured values of SHBG-T and nonbound T. Serum T levels did not change in normal women examined during the follicular and luteal phases of the menstrual cycle, but SHBG levels were elevated in the luteal phase, changing the distribution of T, with increased SHBG-T and less T distributed to other fractions. Women taking oral contraceptives had decreased serum T levels, but use of androgen-like oral contraceptives decreased SHBG levels and T distribution to this binding protein, whereas use of non-androgen-like oral contraceptives increased SHBG levels, resulting in the expected shift of T fractions. Women receiving phenytoin for seizure disorders and women with Graves' disease exhibited increased SHBG levels with concomitant increased SHBG-T and decreased distribution of T to nonbound fractions. Women with hirsutism exhibited decreased SHBG levels irrespective of total serum T levels, and the T/SHBG ratio was elevated in this population. However, of interest were women with morbid obesity (nonhirsute) who had similar low levels of SHBG and T/SHBG ratios that were indistinguishable from those of hirsute women.(ABSTRACT TRUNCATED AT 250 WORDS)