Determination of testosterone and its tissue metabolites (DHT and 3 alpha-diol) in human plasma and prostatic tissue by isotopic dilution mass spectrometry.

5α-Dihydrotestosterone has been widely measured in human prostatic tissue using RIA since it is involved in the pathogenesis of human prostatic hyperplasia and seems to be the best index for the follow-up of patients affected by prostatic cancer under endocrine treatment. A GC-MS method for the simultaneou determination of testosterone (T), 5α-dihydrotestosterone (DHT) and 5α-androstan-3α, 17β-diol (3α-diol) in prostatic tissue based on the isotopic dilution technique was developed. Tri-deuterated internal standards of each compound were previously synthetized in our laboratory. After extraction and purification on Sep-Pak C 18 and Sephadex LH-20, T and its metabolites were measured as heptafluorobutyric ester (HFB) derivatives. Quantitative analysis was performed on a VG 7070 EQ mass spectromer equipped with a fused silica capillary column using the Selected Ion Monitoring technique. Steroid values (mean ± SD; ng/g tissue) found in nine human hypertrophic prostates were: T: 0.71 ± 0.43; DHT: 4.46 ± 1.41; 3α-diol: 0.34 ± 0.23. Preliminary results obtained from the detection of the three androgens in human prostatic hyperplasia treated for 3 months with GnRH before surgery seem to indicate that DHT concentration decreases more than 10 times. Values obtained (n = 1; ng/g tissue) were: T: 0.194; DHT: 0.255; 3α-diol: 0.015.