D3 testosterone

Standards for the analytes examined in this study (see Table 1 and Fig. 1) were purchased from Steraloids (Newport, RI, USA): 17a-hydroxyprogesterone (17OH-progesterone), 5a-DHP, allopregnanolone (3aDHP), androstenedione, DHEA, d 7 -androstendione (A 4 -d 7 ), estrone, pregnenolone, 5a-pregnan-3b, 20a-diol (3b,20a-dihydroxy-dihydroprogesterone (3b,20a-DHP)), 20a-hydroxy-5a-DHP (20a-hydroxy-dihydroprogesterone (20aDHP)), progesterone and d 9 -progesterone (P 4 -d 9 ). The remaining analytes were purchased from Cerilliant (Round Rock, TX, USA): 19-norandrostenedione, 5a-dihydrotestosterone (DHT), d 3 -testosterone (T-d 3 ), and testosterone. A master mix of all reference standards was prepared and diluted in methanol (10, 1, 0.1 and 0.01 ng/ml). Methanol and water were of HPLC grade and obtained from Burdick and Jackson (Muskegon, MI, USA). Formic acid and methyl-tert buytl ether were of ACS grade and obtained from EMD (Gibbstown, NJ, USA).