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The beneficial effect of L-thyroxine on cardiovascular risk factors, endothelial function, and quality of life in subclinical hypothyroidism: Randomized, crossover trial

Lookup NU author(s): Dr Salman Razvi, Lorna Ingoe, Crispian Oates, Dr Jolanta Weaver


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Context: Subclinical hypothyroidism (SCH) is defined as raised serum TSH levels with circulating thyroid hormones within the reference range. It is uncertain whether treatment of SCH with L-thyroxine improves cardiovascular (CV) risk factors and quality of life. Objective: The objective of the study was to assess CV risk factors and patient-reported outcomes after treatment. Design: This was a randomized, double-blind, crossover study of L-thyroxine and placebo. Setting: The study was conducted with community-dwelling patients. Patients: One hundred patients [mean age (SD) 53.8 (12) yr, 81 females] with SCH [mean TSH 6.6 (1.3) mIU/liter] without previously treated thyroid or vascular disease. Intervention: Intervention consisted of 100 μg L-thyroxine or placebo daily for 12 wk each. Measurements: Primary parameters were total cholesterol (TC) and endothelial function [brachial artery flow-mediated dilatation (FMD)], an early marker of atherosclerosis. Patient-reported outcomes were also assessed. Results: L-thyroxine treatment reduced TC (vs. placebo) from 231.6 to 220 mg/dl, P < 0.001; low-density lipoprotein cholesterol from 142.9 to 131.3 mg/dl, P < 0.05; waist to hip ratio from 0.83 to 0.81, P < 0.006; and improved FMD from 4.2 to 5.9%, P < 0.001. Multivariate analysis showed that increased serum free T4 level was the most significant variable predicting reduction in TC or improvement in FMD. Furthermore, the symptom of tiredness improved on L-thyroxine therapy, but other patient-reported outcomes were not significantly different after correction for multiple comparisons. Conclusion: SCH treated by L-thyroxine leads to a significant improvement in CV risk factors and symptoms of tiredness. The CV risk factor reduction is related to the increased level of achieved free T4 concentration. Copyright © 2007 by The Endocrine Society.

Publication metadata

Author(s): Razvi S, Ingoe L, Keeka G, Oates C, McMillan C, Weaver JU

Publication type: Article

Publication status: Published

Journal: Journal of Clinical Endocrinology and Metabolism

Year: 2007

Volume: 92

Issue: 5

Pages: 1715-1723

ISSN (print): 0021-972X

ISSN (electronic): 1945-7197

Publisher: The Endocrine Society


DOI: 10.1210/jc.2006-1869

PubMed id: 17299073


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