Published ; Journal Article ; Meta-Analysis ; Research Support, N.I.H., Extramural ; Research Support, N.I.H., Intramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S. ; Thyroid hormone is essential for normal metabolism and development, and overt abnormalities in thyroid function lead to common endocrine disorders affecting approximately 10% of individuals over their life span. In addition, even mild alterations in thyroid function are associated with weight changes, atrial fibrillation, osteoporosis, and psychiatric disorders. To identify novel variants underlying thyroid function, we performed a large meta-analysis of genome-wide association studies for serum levels of the highly heritable thyroid function markers TSH and FT4, in up to 26,420 and 17,520 euthyroid subjects, respectively. Here we report 26 independent associations, including several novel loci for TSH (PDE10A, VEGFA, IGFBP5, NFIA, SOX9, PRDM11, FGF7, INSR, ABO, MIR1179, NRG1, MBIP, ITPK1, SASH1, GLIS3) and FT4 (LHX3, FOXE1, AADAT, NETO1/FBXO15, LPCAT2/CAPNS2). Notably, only limited overlap was detected between TSH and FT4 associated signals, in spite of the feedback regulation of their circulating levels by the hypothalamic-pituitary-thyroid axis. Five of the reported loci (PDE8B, PDE10A, MAF/LOC440389, NETO1/FBXO15, and LPCAT2/CAPNS2) show strong gender-specific differences, which offer clues for the known sexual dimorphism in thyroid function and related pathologies. Importantly, the TSH-associated loci contribute not only to variation within the normal range, but also to TSH values outside the reference range, suggesting that they may be involved in thyroid dysfunction. Overall, our findings explain, respectively, 5.64% and 2.30% of total TSH and FT4 trait variance, and they improve the current knowledge of the regulation of hypothalamic-pituitary-thyroid axis function and the consequences of genetic variation for hypo- or hyperthyroidism. ; Intramural Research Program of the NIH ; NCRR ; NHLBI ; MedStar Research Institute ; NINDS ; National Center of Advancing Translational Technologies CTSI ; National Institute of Diabetes and Digestive and Kidney Diseases ; Robert Dawson Evans Endowment ; Italian Ministry of Health ; University and Research of the Autonomous Province of Bolzano ; European Union's Seventh Framework Programme ; ENGAGE project ; EPIGENESYS ; BLUEPRINT ; Dutch Innovation-Oriented Research Program on Genomics ; Netherlands Organization for Scientific Research (NWO) ; South Tyrolean Sparkasse Foundation ; Radboud University Nijmegen Medical Centre ; University of Maryland General Clinical Research Center ; Johns Hopkins University General Clinical Research Center ; Baltimore Veterans Administration Geriatric Research and Education Clinical Center (GRECC) ; Netherlands Research Institute for Diseases in the Elderly ; Erasmus Medical Center and Erasmus University, Rotterdam ; Netherlands Organization for the Health Research and Development (ZonMw) ; Dutch Ministry for Health, Welfare and Sports ; European Commission ; Municipality of Rotterdam ; German Bundesministerium fuer Forschung und Technology ; Wellcome Trust ; English Department of Health, National Institute for Health Research (NIHR) Comprehensive Biomedical Research Centre ; Canadian Institutes of Health Research, Canadian Foundation for Innovation ; Fonds de la Recherche en Santé Québec, Ministère du Développement Économique, de l'Innovation et de l'Exportation ; Lady Davis Institute of the Jewish General Hospital (JBR) ; Australian National Health and Medical Research Council ; Sir Charles Gairdner Hospital Research Fund ; Italian “Compagnia di San Paolo” ; Italian “Fondazione Cariplo” ; Leiden University Medical Centre ; Dutch Arthritis Association ; Pfizer, Groton, CT, USA ; Dutch Centre of Medical System Biology ; Netherlands Genomics Initiative (NGI), Netherlands Consortium of Healthy Aging ; Academy of Finland ; Finnish Diabetes Research Society ; Folkhälsan Research Foundation ; Novo Nordisk Foundation ; Finska Läkaresällskapet, Signe and Ane Gyllenberg Foundation ; University of Helsinki ; European Science Foundation (EUROSTRESS) ; Finnish Ministry of Education ; Ahokas Foundation ; Emil Aaltonen Foundation ; Juho Vainio Foundation ; BBSRC ; EPSRC ; ESRC ; MRC ; AXA Research Fund ; Help the Aged/Research Into Ageing (Disconnected Mind) ; Economic Structure Enhancing Fund (FES) of the Dutch government ; Dutch Ministry of Economic Affairs ; Dutch Ministry of Education, Culture and Science ; Northern Netherlands Collaboration of Provinces (SNN) ; Province of Groningen ; University of Groningen ; Dutch Kidney Foundation ; Dutch Diabetes Research Foundation ; Bristol-Myers Squibb ; Netherlands Heart Foundation ; National Computing Facilities Foundation (NCF), Netherlands ; Endocrine Research Fund