Modulatory Effect of Raloxifene and Estrogen on the Metabolic Action of Growth Hormone in Hypopituitary Women

Context: The metabolic action of GH is attenuated by estrogens administered via the oral route. Selective estrogen receptor modulators lower IGF-I to a lesser degree than 17β-estradiol in GH-deficient women, and their effect on fat and protein metabolism is unknown. Objective: The aim of the study was to compare the modulatory effects of 17β-estradiol and raloxifene, a selective estrogen receptor modulator, on the metabolic action of GH. Design: We conducted an open-label, two-group, randomized, two-period crossover study. Patients and Intervention: Ten hypopituitary women received GH therapy alone (0.5 mg/d) and GH plus 17β-estradiol (E2; 2 mg/d). Eleven hypopituitary women received GH therapy alone and GH plus raloxifene (R; 60 mg/d). The treatment duration was 1 month, with a 4-wk washout period. Main Outcome Measures: IGF-I, IGFBP-3, resting energy expenditure, and fat oxidation were quantified by indirect calorimetry. We measured whole body leucine turnover from which leucine rate of appearance and l...