Subclinical thyroid dysfunction and circulating thyroid hormones are not associated with bone turnover markers or incident hip fracture in older men

ObjectiveOvert thyroid dysfunction is a risk factor for osteoporosis and fractures. Subclinical hyperthyroidism has also been associated with fracture. It remains unclear whether variation in thyroid hormones within the euthyroid range modulates bone health, particularly among older men. We assessed whether thyroid stimulating hormone (TSH) and free thyroxine (FT4) are associated with bone turnover markers (BTMs) and predict hip fracture risk in community-dwelling older men without known thyroid disease. DesignProspective cohort study. PatientsFour thousand two hundred forty-eight men aged 70-89years. MeasurementsBaseline blood samples were assayed for TSH, FT4, total osteocalcin (TOC), undercarboxylated osteocalcin (ucOC), N-terminal propeptide of type I collagen (P1NP) and collagen type I C-terminal cross-linked telopeptide (CTX). Incidence of hip fracture events was ascertained to 2012. Associations of TSH and FT4 with BTMs were analysed at baseline using Pearson correlation coefficients, and with incident hip fracture using Cox proportional hazards regression. ResultsAfter excluding men with pre-existing thyroid or bone disease, there were 3, 338 men for analysis. Of these, 3, 117 were euthyroid, 135 had subclinical hypothyroidism, and 86 had subclinical hyperthyroidism. Men with subclinical thyroid disease were older, and those with subclinical hyperthyroidism had lower creatinine than the other groups. After multivariate analysis, there were no associations found between FT4, TSH or subclinical thyroid dysfunction and BTMs at baseline. Neither subclinical thyroid dysfunction, TSH nor FT4 were predictive of incident hip fracture in our study population. ConclusionsIn euthyroid older men, TSH and FT4 were not associated with BTMs or incident hip fracture. Our findings differ from those previously described in postmenopausal women.