Synthesis of new steroid haptens for radioimmunoassay—VIII. Development and validation of a specific radioimmunoassay for serum 5α-androstane-3α,17β-diol 17-glucuronide

5α-Androstane-3α,17β-diol glucuronide (androstanediol-G) is a dihydrotestosterone metabolite whose serum levels are elevated in hirsute women. Current assay methods do not distinguish between the two androstanediol-G isomers, androstanediol 3-G and androstanediol 17-G. Since the production of these isomers may be influenced by different factors, we have developed a specific radioimmunoassay for androstanediol 17G. The antibody was raised against 5α-androstane-3α,17β-diol 17-G conjugated to bovine serum albumin (BSA). [9,11-³H]5α-Androstane-3α,17β-diol 17-G was used for determination of procedural losses and as the labeled ligand in the assay. Unlabeled androstanediol 17-G was used as assay standard.

Serum levels of total androstanediol-G, androstanediol 3-G and androstanediol 17-G were measured in 8 normal men. Total androstanediol-G levels were 16.5 ± 5.2 nmol/l, androstanediol 17-G levels were 12.9 ± 5 nmol/l, and androstanediol 3-G levels were 30.3 ± 1.8 nmol/l. 77 ± 13% of total androstanediol-G was androstanediol 17-G.

These results confirm our previous findings that androstanediol 17-G is the predominant androstanediol-G isomer in human serum and suggests that 5α-dihydrotestosterone (DHT) is preferentially metabolized to androstanediol 17-G.