Conversion of dihydrotestosterone to androstanediol glucuronide by female sexual skin

Clinical biochemistry of dihydrotestosterone

Dihydrotestosterone (DHT) is the most potent natural androgen in humans. There has been an increasing interest in this androgen and its role in the development of primary and secondary sexual characteristics as well as its potential roles in diseases ranging from prostate and breast cancer to Alzheimer's disease. Despite the range of pathologies shown to involve DHT there is little evidence for measurement of serum DHT in the management of these diseases. In this review we describe the physiology of DHT production and action, summarize current concepts in the role of DHT in the pathogenesis of various disorders of sexual development, compare current methods for the measurement of DHT and conclude on the clinical utility of DHT measurement. The clinical indications for the measurement of DHT in serum are: investigation of 5α reductase deficiency in infants with ambiguous genitalia and palpable gonads; men with delayed puberty and/or undescended testes; and to confirm the presence of active testicular tissue. Investigation is aided by the use of human chorionic gonadotrophin stimulation. Due to paucity of published data on this procedure, it is important to follow guidelines prescribed by the laboratory performing the analysis to ensure accurate interpretation.

Inactivation of androgens by UDP-glucuronosyltransferase enzymes in humans

In humans, 3beta-hydroxysteroid dehydrogenase (3beta-HSD), 17beta-HSD and 5alpha-reductase activities in androgen target tissues, such as the prostate and skin, convert dehydroepiandrosterone, androstenedione and testosterone into the most potent natural androgen dihydrotestosterone (DHT). This androgen is converted mainly in situ into two phase I metabolites, androsterone (ADT) and androstane-3alpha,17beta-diol (3alpha-DIOL), which might be back converted to DHT. Here, we discuss the recent findings regarding the characterization of specific UDP-glucuronosyltransferases (UGTs), UGT2B7, B15 and B17, responsible for the glucuronidation of these metabolites. The tissue distribution and cellular localization of the UGT2B transcripts and proteins in humans clearly indicate that these enzymes are synthesized in androgen-sensitive tissues. It is postulated that the conjugating activity of UGT enzymes is the main mechanism for modulating the action of steroids and protecting the androgen-sensitive tissues from deleteriously high concentrations of DHT, ADT and 3alpha-DIOL.

Serum levels of androstanediol glucuronide, total testosterone, and free testosterone in hirsute women

OBJECTIVE

To determine the serum levels of androstanediol glucuronide (3 alpha-diol G), total T, and free T in hirsute and nonhirsute women.

DESIGN

Controlled clinical study.

PATIENTS

Hirsute women with oligomenorrhea, hirsute women with regular ovulatory cycles, and nonhirsute women with regular cycles were selected.

MAIN OUTCOME MEASURE

Serum levels of 3 alpha-diol G, total T, and free T were measured in 8 hirsute with oligomenorrhea and 11 hirsute women with regular ovulatory cycles and compared with 20 nonhirsute women with regular cycles (control group). Serum 3 alpha-diol G was also measured during the follicular, periovulatory, and luteal phases in hirsute women with regular cycles.

RESULTS

Serum levels of 3 alpha-diol G did not change during the menstrual cycle, in addition we observed that there was no difference between the levels of 3 alpha-diol G, total T, and free T in hirsute women with regular cycles when compared with normal women. These three serum androgens were elevated only in the hirsute women with oligomenorrhea. Besides, there was better correlation between total T and free T (r = 0.81) than total T and 3 alpha-diol G (r = 0.49) or free T and 3 alpha-diol G (r = 0.66).

CONCLUSION

The findings suggest that serum 3 alpha-diol G does not provide additional benefit as a marker of hirsutism than serum total or free T.