@article {6800, title = {Subclinical Hypothyroidism and the Risk of Stroke Events and Fatal Stroke: An Individual Participant Data Analysis.}, journal = {J Clin Endocrinol Metab}, volume = {100}, year = {2015}, month = {2015 Jun}, pages = {2181-91}, abstract = {

OBJECTIVE: The objective was to determine the risk of stroke associated with subclinical hypothyroidism.

DATA SOURCES AND STUDY SELECTION: Published prospective cohort studies were identified through a systematic search through November 2013 without restrictions in several databases. Unpublished studies were identified through the Thyroid Studies Collaboration. We collected individual participant data on thyroid function and stroke outcome. Euthyroidism was defined as TSH levels of 0.45-4.49 mIU/L, and subclinical hypothyroidism was defined as TSH levels of 4.5-19.9 mIU/L with normal T4 levels.

DATA EXTRACTION AND SYNTHESIS: We collected individual participant data on 47 573 adults (3451 subclinical hypothyroidism) from 17 cohorts and followed up from 1972-2014 (489 192 person-years). Age- and sex-adjusted pooled hazard ratios (HRs) for participants with subclinical hypothyroidism compared to euthyroidism were 1.05 (95\% confidence interval [CI], 0.91-1.21) for stroke events (combined fatal and nonfatal stroke) and 1.07 (95\% CI, 0.80-1.42) for fatal stroke. Stratified by age, the HR for stroke events was 3.32 (95\% CI, 1.25-8.80) for individuals aged 18-49 years. There was an increased risk of fatal stroke in the age groups 18-49 and 50-64 years, with a HR of 4.22 (95\% CI, 1.08-16.55) and 2.86 (95\% CI, 1.31-6.26), respectively (p trend 0.04). We found no increased risk for those 65-79 years old (HR, 1.00; 95\% CI, 0.86-1.18) or >= 80 years old (HR, 1.31; 95\% CI, 0.79-2.18). There was a pattern of increased risk of fatal stroke with higher TSH concentrations.

CONCLUSIONS: Although no overall effect of subclinical hypothyroidism on stroke could be demonstrated, an increased risk in subjects younger than 65 years and those with higher TSH concentrations was observed.

}, keywords = {Adult, Asymptomatic Diseases, Female, Humans, Hypothyroidism, Incidence, Male, Risk Factors, Stroke, Thyrotropin}, issn = {1945-7197}, doi = {10.1210/jc.2015-1438}, author = {Chaker, Layal and Baumgartner, Christine and den Elzen, Wendy P J and Ikram, M Arfan and Blum, Manuel R and Collet, Tinh-Hai and Bakker, Stephan J L and Dehghan, Abbas and Drechsler, Christiane and Luben, Robert N and Hofman, Albert and Portegies, Marileen L P and Medici, Marco and Iervasi, Giorgio and Stott, David J and Ford, Ian and Bremner, Alexandra and Wanner, Christoph and Ferrucci, Luigi and Newman, Anne B and Dullaart, Robin P and Sgarbi, Jos{\'e} A and Ceresini, Graziano and Maciel, Rui M B and Westendorp, Rudi G and Jukema, J Wouter and Imaizumi, Misa and Franklyn, Jayne A and Bauer, Douglas C and Walsh, John P and Razvi, Salman and Khaw, Kay-Tee and Cappola, Anne R and V{\"o}lzke, Henry and Franco, Oscar H and Gussekloo, Jacobijn and Rodondi, Nicolas and Peeters, Robin P} } @article {7550, title = {Thyroid Function Within the Normal Range, Subclinical Hypothyroidism, and the Risk of Atrial Fibrillation.}, journal = {Circulation}, volume = {136}, year = {2017}, month = {2017 Nov 28}, pages = {2100-2116}, abstract = {

BACKGROUND: Atrial fibrillation (AF) is a highly prevalent disorder leading to heart failure, stroke, and death. Enhanced understanding of modifiable risk factors may yield opportunities for prevention. The risk of AF is increased in subclinical hyperthyroidism, but it is uncertain whether variations in thyroid function within the normal range or subclinical hypothyroidism are also associated with AF.

METHODS: We conducted a systematic review and obtained individual participant data from prospective cohort studies that measured thyroid function at baseline and assessed incident AF. Studies were identified from MEDLINE and EMBASE databases from inception to July 27, 2016. The euthyroid state was defined as thyroid-stimulating hormone (TSH) 0.45 to 4.49 mIU/L, and subclinical hypothyroidism as TSH 4.5 to 19.9 mIU/L with free thyroxine (fT4) levels within reference range. The association of TSH levels in the euthyroid and subclinical hypothyroid range with incident AF was examined by using Cox proportional hazards models. In euthyroid participants, we additionally examined the association between fT4 levels and incident AF.

RESULTS: Of 30 085 participants from 11 cohorts (278 955 person-years of follow-up), 1958 (6.5\%) had subclinical hypothyroidism and 2574 individuals (8.6\%) developed AF during follow-up. TSH at baseline was not significantly associated with incident AF in euthyroid participants or those with subclinical hypothyroidism. Higher fT4 levels at baseline in euthyroid individuals were associated with increased AF risk in age- and sex-adjusted analyses (hazard ratio, 1.45; 95\% confidence interval, 1.26-1.66, for the highest quartile versus the lowest quartile of fT4; P for trend <=0.001 across quartiles). Estimates did not substantially differ after further adjustment for preexisting cardiovascular disease.

CONCLUSIONS: In euthyroid individuals, higher circulating fT4 levels, but not TSH levels, are associated with increased risk of incident AF.

}, keywords = {Adult, Aged, Aged, 80 and over, Asymptomatic Diseases, Atrial Fibrillation, Biomarkers, Chi-Square Distribution, Female, Humans, Hypothyroidism, Incidence, Male, Middle Aged, Predictive Value of Tests, Prognosis, Proportional Hazards Models, Risk Assessment, Risk Factors, Thyroid Function Tests, Thyroid Gland, Thyrotropin, Thyroxine, Time Factors, Young Adult}, issn = {1524-4539}, doi = {10.1161/CIRCULATIONAHA.117.028753}, author = {Baumgartner, Christine and da Costa, Bruno R and Collet, Tinh-Hai and Feller, Martin and Floriani, Carmen and Bauer, Douglas C and Cappola, Anne R and Heckbert, Susan R and Ceresini, Graziano and Gussekloo, Jacobijn and den Elzen, Wendy P J and Peeters, Robin P and Luben, Robert and V{\"o}lzke, Henry and D{\"o}rr, Marcus and Walsh, John P and Bremner, Alexandra and Iacoviello, Massimo and Macfarlane, Peter and Heeringa, Jan and Stott, David J and Westendorp, Rudi G J and Khaw, Kay-Tee and Magnani, Jared W and Aujesky, Drahomir and Rodondi, Nicolas} }