Association of thyroid function with estimated glomerular filtration rate in a population-based study: the HUNT study

Abstract

ObjectiveLow thyroid function may be associated with reduced glomerular filtration rate (GFR). We therefore studied the association of thyroid function with estimated GFR (eGFR) in a population-based study.DesignA cross-sectional, population-based study of 29 480 individuals above 40 years of age, without previously known thyroid disease.MethodsWe calculated geometric mean eGFR and odds ratio (OR) of chronic kidney disease (CKD; eGFR <60 ml/min per 1.73 m2) according to categories of thyroid function, using people with TSH in the lower third of the reference range (0.50–1.4 mU/l) as the comparison group.ResultsTSH within the reference range (0.50–3.5 mU/l) was negatively associated with eGFR (Pfor trend <0.001). Compared with people with TSH in the lower third of the reference range (83.0 ml/min per 1.73 m2), eGFR was lower in people with TSH in the middle (81.6 ml/min per 1.73 m2) and highest third (80.3 ml/min per 1.73 m2) of the reference range, and in people with subclinical (79.3 ml/min per 1.73 m2,P<0.001) or overt hypothyroidism (76.5 ml/min per 1.73 m2,P<0.001). The prevalence of CKD was higher in people with TSH in the middle (OR 1.20, 95% confidence interval (CI) 1.07–1.35) or highest third (OR 1.31, 95% CI 1.13–1.52) of the reference range, compared with people in the reference group. Also, CKD was more common in people with subclinical (OR 1.63, 95% CI 1.38–1.93) or overt (OR 1.98, 95% CI 1.22–3.20) hypothyroidism.ConclusionsThese findings suggest that low thyroid function, also within the clinically normal range, is associated with reduced GFR.