Stable isotope dilution analysis of human urinary metabolites of 17alpha-methyltestosterone

A method based on gas chromatography-mass spectrometry-selected-ion monitoring was developed to measure the main metabolites of 17alpha-methyltestosterone, 17alpha-methyl-5alpha-androstan-3alpha,17beta-di ol and 17alpha-methyl-5beta-androstan-3alpha,17beta-dio l, in human urine. 17alpha-Methyl-[(2)H3]-5alpha-androstan-3alpha,1 7beta-diol and 17alpha-methyl-[(2)H3]-5beta-androstan-3alpha,17 beta-diol were used as internal standards. The methods involved purification using a Sep-Pak C(18) cartridge, hydrolysis by beta-glucuronidase from Ampullaria and derivatization with N-methyl-N-trimethylsilyl-trifluoroacetamide/dithioerythriol/ammon ium iodide. Quantitation was achieved by selected-ion monitoring of the characteristic fragment ions ([(M+H)-2xTMSOH]+) of the di-TMS derivatives on the chemical ionization mode. The method provides a specific, sensitive and reliable technique to determine the urine levels of 17alpha-methyl-5alpha-androstan-3alpha,17beta-di ol and 17alpha-methyl-5beta-androstan-3alpha,17beta-dio l, and can be applied to pharmacokinetic studies of 17alpha-methyltestosterone.