Higher free thyroxine levels are associated with frailty in older men: the Health In Men Study

Objective Frailty is common in the elderly and predisposes to ill-health. Some symptoms of frailty overlap those of thyroid dysfunction, but it is unclear whether differences in thyroid status influence risk of frailty. We evaluated associations between thyroid status and frailty in older men. Design Cross-sectional epidemiological study. Participants Community-dwelling men aged 70-89 years. Measurements Circulating thyrotropin (TSH) and free thyroxine (FT4) were assayed. Frailty was assessed as 3 of the Fatigue, Resistance, Ambulation, Illnesses and Loss (FRAIL) scale's 5 domains: fatigue; resistance (difficulty climbing flight of stairs); ambulation (difficulty walking 100 m); illness (>5); or weight loss (>5%), blinded to hormone results. Results Of 3943 men, 27 had subclinical hyperthyroidism, 431 subclinical hypothyroidism and 608 were classified as being frail (15.4%). There was an inverse log-linear association of TSH with FT4. There was no association between TSH and frailty. After adjusting for covariates, men with FT4 in the highest two quartiles had increased odds of being frail (Q3:Q1, odds ratio [OR] = 1.32, 95% confidence interval [CI] = 1.01-1.73 and Q4:Q1, OR = 1.36, 95% CI = 1.04-1.79, P = 0.010 for trend). Higher FT4 was associated with fatigue (P = 0.038) and weight loss (P < 0.001). The association between FT4 and frailty remained significant when the analysis was restricted to euthyroid men. Conclusions High-normal FT4 level is an independent predictor of frailty among ageing men. This suggests that even within the euthyroid range, circulating thyroxine may contribute to reduced physical capability. Further studies are needed to clarify the utility