B M Arafah1. 1. Division of Clinical and Molecular Endocrinology, Case Western Reserve University and the University Hospitals of Cleveland, OH 44106, USA.
Abstract
BACKGROUND: Women with hypothyroidism that is being treated with thyroxine often need higher doses when they are pregnant. Whether this need can be attributed solely to estrogen-induced increases in serum thyroxine-binding globulin or whether other factors are involved is not known. METHODS: In 11 postmenopausal women with normal thyroid function and 25 postmenopausal women with hypothyroidism treated with thyroxine, I assessed thyroid function before they started estrogen therapy and every 6 weeks for 48 weeks thereafter. The women with hypothyroidism included 18 women receiving thyroxine-replacement therapy and 7 women receiving thyrotropin-suppressive thyroxine therapy. On each occasion, serum thyroxine, free thyroxine, thyrotropin, and thyroxine-binding globulin were measured. RESULTS: In the women with normal thyroid function, the serum free thyroxine and thyrotropin concentrations did not change, whereas at 12 weeks the mean (+/-SD) serum thyroxine concentration had increased from 8.0+/-0.9 microg per deciliter (103+/-12 nmol per liter) to 10.4+/-1.5 microg per deciliter (134+/-19 nmol per liter, P<0.001) and the serum thyroxine-binding globulin concentration had increased from 20.3+/-3.5 mg per liter to 31.3+/-3.2 mg per liter, P<0.001). The women with hypothyroidism had similar increases in serum thyroxine and thyroxine-binding globulin concentrations during estrogen therapy, but their serum free thyroxine concentration decreased from 1.7+/-0.4 ng per deciliter (22+/-5 pmol per liter) to 1.4+/-0.3 ng per deciliter (18+/-4 pmol per liter, P<0.001) and their serum thyrotropin concentration increased from 0.9+/-1.1 to 3.2+/-3.1 microU per milliliter (P<0.001). The serum thyrotropin concentrations increased to more than 7 microU per milliliter in 7 of the 18 women in the thyroxine-replacement group and to more than 1 microU per milliliter in 3 of the 7 women in the thyrotropin-suppression group. CONCLUSIONS: In women with hypothyroidism treated with thyroxine, estrogen therapy may increase the need for thyroxine.
BACKGROUND:Women with hypothyroidism that is being treated with thyroxine often need higher doses when they are pregnant. Whether this need can be attributed solely to estrogen-induced increases in serum thyroxine-binding globulin or whether other factors are involved is not known. METHODS: In 11 postmenopausal women with normal thyroid function and 25 postmenopausal women with hypothyroidism treated with thyroxine, I assessed thyroid function before they started estrogen therapy and every 6 weeks for 48 weeks thereafter. The women with hypothyroidism included 18 women receiving thyroxine-replacement therapy and 7 women receiving thyrotropin-suppressive thyroxine therapy. On each occasion, serum thyroxine, free thyroxine, thyrotropin, and thyroxine-binding globulin were measured. RESULTS: In the women with normal thyroid function, the serum free thyroxine and thyrotropin concentrations did not change, whereas at 12 weeks the mean (+/-SD) serum thyroxine concentration had increased from 8.0+/-0.9 microg per deciliter (103+/-12 nmol per liter) to 10.4+/-1.5 microg per deciliter (134+/-19 nmol per liter, P<0.001) and the serum thyroxine-binding globulin concentration had increased from 20.3+/-3.5 mg per liter to 31.3+/-3.2 mg per liter, P<0.001). The women with hypothyroidism had similar increases in serum thyroxine and thyroxine-binding globulin concentrations during estrogen therapy, but their serum free thyroxine concentration decreased from 1.7+/-0.4 ng per deciliter (22+/-5 pmol per liter) to 1.4+/-0.3 ng per deciliter (18+/-4 pmol per liter, P<0.001) and their serum thyrotropin concentration increased from 0.9+/-1.1 to 3.2+/-3.1 microU per milliliter (P<0.001). The serum thyrotropin concentrations increased to more than 7 microU per milliliter in 7 of the 18 women in the thyroxine-replacement group and to more than 1 microU per milliliter in 3 of the 7 women in the thyrotropin-suppression group. CONCLUSIONS: In women with hypothyroidism treated with thyroxine, estrogen therapy may increase the need for thyroxine.
Authors: Jacqueline Jonklaas; Antonio C Bianco; Andrew J Bauer; Kenneth D Burman; Anne R Cappola; Francesco S Celi; David S Cooper; Brian W Kim; Robin P Peeters; M Sara Rosenthal; Anna M Sawka Journal: Thyroid Date: 2014-12 Impact factor: 6.568
Authors: Kristin A Ojomo; David F Schneider; Alexandra E Reiher; Ngan Lai; Sarah Schaefer; Herbert Chen; Rebecca S Sippel Journal: J Am Coll Surg Date: 2013-01-11 Impact factor: 6.113