This Article Full Text Full Text (PDF) Submit a related Letter to the Editor Purchase Article View Shopping Cart Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Marqusee, E. Articles by Seely, E. W. Search for Related Content PubMed PubMed Citation Articles by Marqusee, E. Articles by Seely, E. W. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB ESTROGENIC SUBSTANCES, CONJUGATED LEVOTHYROXINE LIOTHYRONINE TAMOXIFEN

The Effect of Droloxifene and Estrogen on Thyroid Function in Postmenopausal Women¹

Thyroid Division (E.M., L.E.B.) and Endocrine and Hypertension Division (J.E.L., J.S.C., E.W.S.), Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115

Address correspondence to: Ellen Marqusee, M.D., Thyroid Division, Department of Medicine, Brigham and Women’s Hospital, Harvard Institutes of Medicine, 77 Avenue Louis Pasteur, Boston, Massachusetts 02115. E-mail: emarqusee{at}bics.bwh.harvard.edu

Abstract

Estrogen is known to increase serum T₄-binding globulin (TBG) concentrations, thereby increasing serum total T₄ concentrations. Serum free T₄ concentrations, however, remain normal. Tamoxifen, a selective estrogen receptor modifier (SERM), also raises serum TBG concentrations, but whether newer SERMs with less stimulatory action on the endometrium do so is not known. We, therefore, compared the effect of droloxifene, a SERM, and conjugated equine estrogen on pituitary-thyroid function in normal postmenopausal women.

Ten women were treated for 6 weeks with conjugated estrogen (Premarin), 0.625 mg/day, and droloxifene, 60 mg/day, in a double-blind crossover study with an intervening 4-week no-treatment period. We measured serum T₄, T₃, TBG, free T₄ index, and TSH at baseline and at the end of each 6-week period. The baseline values were compared with the 6-week values using paired t tests.

The mean (±SD) serum TBG concentrations increased significantly during both treatment periods (baseline, 1.5 ± 0.4 mg/dL; conjugated estrogens, 2.7 ± 0.6 mg/dL; droloxifene, 2.1 ± 0.6 mg/dL; P < 0.001 and P = 0.001, respectively). There were no significant changes in the serum free T₄ index. Serum T₄ and T₃ concentrations increased during both treatment periods, however, the increase was significant only for T₄ during the conjugated estrogen treatment period. The serum TSH concentrations increased significantly during both treatment periods (18% during conjugated estrogen and 11% during droloxifene), and the values remained within the normal range in all women.

Administration of both conjugated estrogen and droloxifene for 6 weeks increases serum TSH and TBG concentrations, but does not alter free T₄ index values in postmenopausal women.

This article has been cited by other articles:

				A. P. Heaney, V. Nelson, M. Fernando, and G. Horwitz Transforming Events in Thyroid Tumorigenesis and Their Association with Follicular Lesions J. Clin. Endocrinol. Metab., October 1, 2001; 86(10): 5025 - 5032. [Abstract] [Full Text] [PDF]