title: Thyroid status and renal function in older persons in the general population.
abstract: BACKGROUND
  Prevalence estimates of thyroid dysfunction and chronic kidney disease both increase with age. The aim of this study was to investigate the cross-sectional association between low thyroid function and renal function in subjects aged 85 years and to assess whether a low thyroid function at age 85 years is associated with an accelerated decline in renal function during follow-up.
  
  
  METHODS
  We included 558 participants from the Leiden 85-plus Study. At baseline (age 85 y), TSH, free T4 (fT4), and free T3 levels were measured. Thyroid function groups were created using clinical cutoff values of TSH and fT4. Serum creatinine concentrations were determined at baseline and annually during a 5-year follow-up period. Estimated glomerular filtration rates (eGFRs) were calculated by means of the Modification of Diet in Renal Disease Study equation.
  
  
  RESULTS
  At baseline, subjects with higher levels of TSH and lower levels of fT4 and free T3 had lower renal function. Participants with hypothyroidism [mean 53.7 (2.0) mL/min per 1.73 m(2))] and subclinical hypothyroidism [55.7 (2.1) mL/min per 1.73 m(2)] had lower mean eGFRs (SE) than participants with normal thyroid function [59.5 (0.7) mL/min per 1.73 m(2)]; the highest eGFR was observed in participants with hyperthyroidism [eGFR 61.5 (3.1) mL/min per 1.73 m(2)] (P for trend = .004). There was no association between thyroid hormone levels at baseline and the change in renal function during follow-up.
  
  
  CONCLUSIONS
  Although low thyroid function was associated with lower renal function at age 85 years, an association between a low thyroid function and change in renal function over time was absent. Our findings question the causal relevance of the thyroid status for the deterioration of renal function in the oldest old.
authors.affiliation: Departments of Clinical Epidemiology (C.L.M., F.W.D.), Public Health and Primary Care (J.G., W.P.J.d.E.), and Gerontology and Geriatrics (A.J.M.d.C.), Leiden University Medical Center, 2300 RC Leiden, The Netherlands.
authors.forename: Christiaan L
authors.initials: CL
authors.lastname: Meuwese
authors.forename: Jacobijn
authors.initials: J
authors.lastname: Gussekloo
authors.forename: Anton J M
authors.initials: AJ
authors.lastname: de Craen
authors.forename: Friedo W
authors.initials: FW
authors.lastname: Dekker
authors.forename: Wendy P J
authors.initials: WP
authors.lastname: den Elzen
mesh_terms: D000367:Age Factors; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007668:Kidney / Q000502:physiology*; D007677:Kidney Function Tests; D008297:Male; D051436:Renal Insufficiency, Chronic / Q000453:epidemiology; D013959:Thyroid Diseases / Q000453:epidemiology; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000502:physiology*