@article {7238, title = {Thyroid Function Within the Reference Range and the Risk of Stroke: An Individual Participant Data Analysis.}, journal = {J Clin Endocrinol Metab}, volume = {101}, year = {2016}, month = {2016 Nov}, pages = {4270-4282}, abstract = {

CONTEXT: The currently applied reference ranges for thyroid function are under debate. Despite evidence that thyroid function within the reference range is related with several cardiovascular disorders, its association with the risk of stroke has not been evaluated previously.

DESIGN AND SETTING: We identified studies through a systematic literature search and the Thyroid Studies Collaboration, a collaboration of prospective cohort studies. Studies measuring baseline TSH, free T4, and stroke outcomes were included, and we collected individual participant data from each study, including thyroid function measurements and incident all stroke (combined fatal and nonfatal) and fatal stroke. The applied reference range for TSH levels was between 0.45 and 4.49 mIU/L.

RESULTS: We collected individual participant data on 43 598 adults with TSH within the reference range from 17 cohorts, with a median follow-up of 11.6 years (interquartile range 5.1-13.9), including 449 908 person-years. Age- and sex-adjusted pooled hazard ratio for TSH was 0.78 (95\% confidence interval [CI] 0.65-0.95 across the reference range of TSH) for all stroke and 0.83 (95\% CI 0.62-1.09) for fatal stroke. For the free T4 analyses, the hazard ratio was 1.08 (95\% CI 0.99-1.15 per SD increase) for all stroke and 1.10 (95\% CI 1.04-1.19) for fatal stroke. This was independent of cardiovascular risk factors including systolic blood pressure, total cholesterol, smoking, and prevalent diabetes.

CONCLUSION: Higher levels of TSH within the reference range may decrease the risk of stroke, highlighting the need for further research focusing on the clinical consequences associated with differences within the reference range of thyroid function.

}, issn = {1945-7197}, doi = {10.1210/jc.2016-2255}, author = {Chaker, Layal and Baumgartner, Christine and den Elzen, Wendy P J and Collet, Tinh-Hai and Ikram, M Arfan and Blum, Manuel R and Dehghan, Abbas and Drechsler, Christiane and Luben, Robert N and Portegies, Marileen L P and Iervasi, Giorgio and Medici, Marco and Stott, David J and Dullaart, Robin P and Ford, Ian and Bremner, Alexandra and Newman, Anne B and Wanner, Christoph and Sgarbi, Jos{\'e} A and D{\"o}rr, Marcus and Longstreth, W T and Psaty, Bruce M and Ferrucci, Luigi and Maciel, Rui M B and Westendorp, Rudi G and Jukema, J Wouter and Ceresini, Graziano and Imaizumi, Misa and Hofman, Albert and Bakker, Stephan J L and Franklyn, Jayne A and Khaw, Kay-Tee and Bauer, Douglas C and Walsh, John P and Razvi, Salman and Gussekloo, Jacobijn and V{\"o}lzke, Henry and Franco, Oscar H and Cappola, Anne R and Rodondi, Nicolas and Peeters, Robin P} }