Paradoxical Relationship Between Body Mass Index and Thyroid Hormone Levels: A Study Using Mendelian Randomization

Peter N Taylor1, Rebecca Richmond1, Neil Davies1

  • 1Thyroid Research Group (P.N.T., O.O., J.W.G., C.M.D.) and Institute of Molecular and Experimental Medicine (A.R.), Cardiff University School of Medicine, Cardiff, CF14 4XN United Kingdom; Medical Research Council Integrative Epidemiology Unit (R.R., N.D., G.D.S., N.J.T.), University of Bristol, Bristol, BS8 2BN United Kingdom; Department of Social and Community Medicine (A.S., A.G., K.N., S.R.), University of Bristol, Bristol, BS8 2BN United Kingdom; Department of Biochemistry (K.S.), Bristol Royal Infirmary University Hospitals Bristol National Health Service Foundation Trust, Bristol, BS2 8HW United Kingdom; Geschäftsleiter Medizinisches Versorgungszentrum Labor Dr. Reising-Ackermann und Kollegen (W.W.), D-04289 Leipzig, Germany; Department of Biochemistry (A.T.), Royal United Hospital, Bath, BA1 3NG United Kingdom; Department of Non-Communicable Disease Epidemiology (D.N.), Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, CF14 4XN United Kingdom; Molecular Endocrinology Group (G.R.W.), Department of Medicine, Imperial College London, London, WC1E 7HT United Kingdom; and Musculoskeletal Research Unit (J.H.T.), University of Bristol, Learning and Research Southmead Hospital, Westbury on Trym, Bristol, BS10 5NB United Kingdom.

Summary

Higher childhood body mass index (BMI) causally increases free T3 (FT3) levels, potentially explaining observed associations. This finding is crucial given rising childhood obesity rates.

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