For this purpose the circadian variability of luteinizing hormone, follicle stimulating hormone, testosterone, 5О± androstan 3О±, 17ОІ diol, 5ОІ androstan 3О±, 17ОІ diol, epitestosterone, 4 androstenedione, androsterone and etiocholanolone were measured on eight subjects four males and four females by gas chromatography mass spectrometry and chemiluminescent immunometric assay techniques before and after oral administration of multiple doses of either tamoxifen 80 mg for 2 days or toremifene 120 mg for 2 days or clomiphene 100 mg for 2 days buy viagra cialis online