OBJECTIVE:Estrogen and androgen administration modulate the pituitary-thyroid axis through alterations in thyroid hormone-binding globulin (TBG) metabolism, but the effects of sex steroids on extrathyroidal thyroxine (T4) to triiodothyronine (T3) conversion in humans are unknown. DESIGN AND METHODS: We studied 36 male-to-female and 14 female-to-male euthyroid transsexuals at baseline and after 4 months of hormonal treatment. Male-to-female transsexuals were treated with cyproterone acetate (CA) 100 mg/day alone (n = 10) or in combination with either oral ethinyl estradiol (or-EE) 100 microg/day (n = 14) or transdermal 17beta-estradiol (td-E) 100 microg twice a week (n = 12). Female-to-male transsexuals were treated with i.m. testosterone 250 mg twice a week. A t-test was used to test for differences within groups and ANOVA with post hoc analysis to test for differences between the groups. RESULTS: Or-EE increased TBG (100 +/- 12%, P < .001) and testosterone decreased TBG (-14 +/- 4%, P = 0.01), but free T4 did not change. Td-E and CA did not affect TBG concentrations. TSH was not different between groups at baseline or after treatment. CA decreased T3/T4 ratios (-9 +/- 3%, P = 0.04), suggesting that T4 to T3 conversion was lower. Testosterone increased T3/T4 ratios (30 +/- 9%, P = 0.02), which probably reflects higher T4 to T3 conversion. CONCLUSION: Oral but not transdermal estradiol increases TBG, whereas testosterone lowers TBG. Testosterone increases T3/T4 ratios. Estradiol does not affect T3/T4 ratios, irrespective of the route of administration.
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OBJECTIVE: Estrogen and androgen administration modulate the pituitary-thyroid axis through alterations in thyroid hormone-binding globulin (TBG) metabolism, but the effects of sex steroids on extrathyroidal thyroxine (T4) to triiodothyronine (T3) conversion in humans are unknown. DESIGN AND METHODS: We studied 36 male-to-female and 14 female-to-male euthyroid transsexuals at baseline and after 4 months of hormonal treatment. Male-to-female transsexuals were treated with cyproterone acetate (CA) 100 mg/day alone (n = 10) or in combination with either oral ethinyl estradiol (or-EE) 100 microg/day (n = 14) or transdermal 17beta-estradiol (td-E) 100 microg twice a week (n = 12). Female-to-male transsexuals were treated with i.m. testosterone 250 mg twice a week. A t-test was used to test for differences within groups and ANOVA with post hoc analysis to test for differences between the groups. RESULTS: Or-EE increased TBG (100 +/- 12%, P < .001) and testosterone decreased TBG (-14 +/- 4%, P = 0.01), but free T4 did not change. Td-E and CA did not affect TBG concentrations. TSH was not different between groups at baseline or after treatment. CA decreased T3/T4 ratios (-9 +/- 3%, P = 0.04), suggesting that T4 to T3 conversion was lower. Testosterone increased T3/T4 ratios (30 +/- 9%, P = 0.02), which probably reflects higher T4 to T3 conversion. CONCLUSION: Oral but not transdermal estradiol increases TBG, whereas testosterone lowers TBG. Testosterone increases T3/T4 ratios. Estradiol does not affect T3/T4 ratios, irrespective of the route of administration.
Authors: Sean Mark Patrick; Natalie Hildegard Aneck-Hahn; Susan Van Wyk; Magdelena Catherina Van Zijl; Mampedi Huma; Christiaan de Jager Journal: Environ Sci Pollut Res Int Date: 2020-02-08 Impact factor: 4.223
Authors: F Lombardo; L Toselli; D Grassetti; D Paoli; P Masciandaro; F Valentini; A Lenzi; L Gandini Journal: J Endocrinol Invest Date: 2013-01-14 Impact factor: 4.256