Session: OR11-Thyroid Hormone Action, Cancer and Clinical Thyroid
Room 109 (BCEC)
Outstanding Abstract Award
Methods:We examined associations between TSH (mIU/L), free T4 (pmol/L), and total T3 (nmol/L) and incidence of hip fracture, atrial fibrillation, dementia, coronary heart disease (CHD), heart failure, and total mortality in 360 US community-dwelling men and women aged 65 years and over who were enrolled in the Cardiovascular Health Study and taking levothyroxine. Cox proportional hazard models were used to examine the relationship between each thyroid test and incident events; TSH was log-transformed. All models were adjusted for age, sex, race, and outcome specific covariates.
Results:Mean age was 74.8 years and 79% were women. Only 51% of these levothyroxine users were euthyroid; 13% had overt hyperthyroidism, 16% had subclinical hyperthyroidism, and 20% had an elevated TSH. There were 28 cases of incident hip fracture. Higher TSH levels were associated with a lower risk of hip fracture (HR 0.84; 95% CI 0.71-0.98, p=0.03 for lnTSH) and, concordantly, higher free T4 levels were associated with a higher risk of hip fracture (HR 2.63, 95% CI 1.26-5.50, p=0.01). There were 31 cases of incident dementia and 57 cases of incident CHD. Higher free T4 levels were associated with a higher risk of dementia (HR 2.57, 95% CI 1.18-5.56), p=0.02) and a lower risk of CHD (HR 0.42, 95% CI 0.19-0.93, p=0.03). There were 57 cases of incident atrial fibrillation and 70 cases of incident heart failure. There were no associations between any thyroid function test and atrial fibrillation or heart failure. There were 122 deaths. Higher total T3 levels were associated with lower risk of mortality (HR 0.35, 95% CI 0.19-0.64, p=0.001), consistent with nonthyroidal illness syndrome.
Conclusions: Higher free T4 concentrations are associated with a higher risk of hip fracture and dementia, and a lower risk of CHD, in older levothyroxine users. Clinical trials are needed to evaluate the optimal target concentrations for thyroid hormone replacement in older people.
Nothing to Disclose: PM, AA, MC, JR, BP, ARC
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