title: Sex steroids and the thyroid.
abstract: Thyroid function is modulated by genetic and environmental causes as well as other illnesses and medications such as gonadal or sex steroids. The latter class of drugs (sex steroids) modulates thyroid function. Gonadal steroids exert their influence on thyroid function primarily by altering the clearance of thyroxine-binding globulin (TBG). While oestrogen administration causes an increase in serum TBG concentration, androgen therapy results in a decrease in this binding protein. These effects of gonadal steroids on TBG clearance and concentration are modulated by the chemical structure of the steroid being used, its dose and the route of administration. Despite the gonadal steroids-induced changes in serum TBG concentrations, subjects with normal thyroid glands maintain clinical and biochemical euthyroidism without changes in their serum free thyroxine (T4) or thyroid-stimulating hormone (TSH) levels. In contrast, the administration of gonadal steroids to patients with thyroid diseases causes significant biochemical and clinical alterations requiring changes in the doses of thyroid medications. Similarly, gonadal steroid therapy might unmask thyroid illness in previously undiagnosed subjects. It would be prudent to assess thyroid function in subjects with thyroid disease 6-8 weeks after gonadal steroid administration or withdrawal.
authors: Division of Clinical and Molecular Endocrinology, Case Western Reserve University, Case Medical Center, 11100 Euclid Ave., Cleveland, OH 44106, USA.
authors: Rundsarah
authors: R
authors: Tahboub
authors: Baha M
authors: BM
authors: Arafah
mesh_terms: D000728:Androgens / Q000494:pharmacology; D004347:Drug Interactions; D004967:Estrogens / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D012739:Gonadal Steroid Hormones / Q000494:pharmacology*; D006801:Humans; D011247:Pregnancy; D020845:Selective Estrogen Receptor Modulators / Q000627:therapeutic use; D013959:Thyroid Diseases / Q000188:drug therapy / Q000503:physiopathology; D013961:Thyroid Gland / Q000187:drug effects* / Q000502:physiology; D013972:Thyrotropin / Q000378:metabolism; D013974:Thyroxine / Q000627:therapeutic use; D056825:Thyroxine-Binding Globulin / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000728:Androgens; D004967:Estrogens; D012739:Gonadal Steroid Hormones; D020845:Selective Estrogen Receptor Modulators; D056825:Thyroxine-Binding Globulin; D013972:Thyrotropin; D013974:Thyroxine