Effects of Toremifene, a Selective Estrogen Receptor Modulator, On
ISSN 2472-1972 Effects of Toremifene, a Selective Estrogen Receptor Modulator, on Spontaneous and Stimulated GH Secretion, IGF-I, and IGF-Binding Proteins in Healthy Elderly Subjects Ferdinand Roelfsema,1 Rebecca J. Yang,2 Paul Y. Takahashi,3 Dana Erickson,4 Cyril Y. Bowers,5 and Johannes D. Veldhuis2 1Department of Internal Medicine, Section of Endocrinology and Metabolism, Leiden University Medical Center, 2333 ZA Leiden, Netherlands; 2Endocrine Research Unit, Mayo School of Graduate Medical Education, Center for Translational Science Activities, Mayo Clinic, Rochester, Minnesota 55905; 3Department of Primary Care Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905; 4Department of Endocrinology, Mayo Clinic, Rochester, Minnesota 55905; and 5Department of Internal Medicine, Tulane University Health Sciences Center, New Orleans, Louisiana 70112 Context: Estrogens amplify spontaneous and stimulated growth hormone (GH) secretion, whereas they diminish GH-dependent insulin-like growth factor (IGF)-I in a dose-dependent manner. Selective es- trogen receptor modulators (SERMs), including tamoxifen and toremifene, are widely adjunctively used in breast and prostate cancer. Although some endocrine effects of tamoxifen are known, few data are available for toremifene. Objective: To explore sex-dependent effects of toremifene on spontaneous 10-hour overnight GH se- cretion, followed by GH-releasing hormone–ghrelin stimulation. Additionally, effects on IGF-I, its binding proteins, and sex hormone–binding globulin (SHBG) were quantified. Participants and Design: Twenty men and 20 women, within an allowableagerangeof50to80years, volunteered for this double-blind, placebo-controlled prospective crossover study. Ten-minute blood sampling was done for 10 hours overnight and then for 2 hours after combined GH-releasing hormone–ghrelin injection. Main Outcome Measures: Pulsatile GH and stimulated GH secretion, and fasting levels of IGF-I, IGF- binding protein (IGFBP)1, IGFBP3, and SHBG.
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