Session: MON 437-470-Non-neoplastic Thyroid Disorders
Poster Board MON-447
Overt thyroid disease and subclinical thyroid dysfunction have been associated with poorer health outcomes, but the relationship between thyroid hormone levels within the reference range and mortality in older adults remains unclear.
We examined associations between circulating free thyroxine (FT4) and thyrotrophin (TSH) with all-cause mortality in older men without thyroid disease.
Prospective longitudinal study.
Community-dwelling men aged 70-89 years resident in Perth, Western Australia, were assessed in 2001-4. Men with thyroid disease or taking thyroid-related medications were excluded from the analysis.
Main outcome measures
Baseline FT4 and TSH levels were assayed (Elecsys 2010 immunoanalyser, Roche Diagnostics Australia, coefficients of variation for FT4 were 4.0% and 5.2% at 14 pmol/L and 37 pmol/L; for TSH 4.5% and 4.2% at 0.4 and 5.0 mIU/L). Incident deaths were ascertained using the Western Australian Data Linkage System. Cox proportional hazards regression was used to examine associations of FT4 and TSH with all-cause mortality. Adjustments were made for age, smoking, body mass index, waist:hip ratio, creatinine, hypertension, diabetes, dyslipidemia and cardiovascular disease.
There were 3,888 men without existing thyroid disease followed for (mean±SD) 6.4±1.5 years, during which time 837 died (21.5%). Men who died had higher baseline FT4 (16.2±2.3 vs 15.8±2.1 pmol/L, p<0.001), but comparable TSH levels (2.4±1.5 vs 2.3±1.5 mIU/L, p=0.335). In the fully-adjusted analysis, higher FT4 predicted all-cause mortality (quartiles Q4 vs Q1-3: FT4 ≥17.32 pmol/L: hazard ratio [HR]=1.21, 95% confidence interval [CI]=1.04-1.42, p=0.015). TSH level did not predict mortality. After excluding men with subclinical hyper- or hypothyroidism there were 3,445 men and 738 died (21.4%). In these euthyroid men, higher FT4 remained independently associated with all-cause mortality (Q4 vs Q1-3: adjusted HR=1.21, 95% CI=1.02-1.42, p=0.026).
In older men not known to have thyroid disease, higher FT4 levels predict all-cause mortality independently of conventional risk factors. After excluding men with subclinical hyper- or hypothyroidism, men with FT4 in the highest quartile experienced higher mortality. Additional research is needed to determine whether this relationship is causal, explore potential underlying mechanisms and clarify the utility of thyroid function testing to stratify mortality risk in ageing men.
Nothing to Disclose: BBY, HA, GJH, LF, PEN, PC
*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm
See more of: Abstracts - Orals, Featured Poster Presentations, and Posters