Lower free triiodothyronine levels within the reference range are associated with higher cardiovascular mortality: An analysis of the NHANES

• Published in: International journal of cardiology 2019-06, Vol.285, p.115-120
• Main Authors: Neves, João Sérgio, Leitão, Lia, Baeta Baptista, Rute, Bigotte Vieira, Miguel, Magriço, Rita, Viegas Dias, Catarina, Oliveira, Ana, Falcão-Pires, Inês, Lourenço, André, Carvalho, Davide, Leite-Moreira, Adelino
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; All-cause mortality; Biomarkers - blood; Cardiovascular Diseases - blood; Cardiovascular Diseases - mortality; Cardiovascular mortality; Cause of Death - trends; Female; Humans; Immunoenzyme Techniques; Male; Middle Aged; Mortality; Nutrition Surveys - methods; Portugal - epidemiology; Reference Values; Retrospective Studies; Risk Assessment - methods; Risk Factors; Survival Rate - trends; Thyroid function; Triiodothyronine; Triiodothyronine - blood; Young Adult
• ISSN: 0167-5273; 1874-1754
• DOI: 10.1016/j.ijcard.2019.03.009

Thyroid hormones play a central role in cardiovascular homeostasis. Lower free triiodothyronine (FT3) levels have been associated with worse prognosis in several conditions. However, contrary to thyrotropin (TSH) and free thyroxine (FT4), the role of FT3 in morbidity and mortality in the general population remains uncertain. Our objective was to evaluate the association between within the normal range FT3 levels and mortality in the general population. We evaluated 7116 adults in the National Health and Nutrition Examination Survey (NHANES) 2001–2002, 2007–2008, and 2009–2010 cycles with mortality evaluated as of December 2011. Exclusion criteria were: pregnancy; history of thyroid disease; use of thyroid-related drugs; and TSH, FT4, or FT3 level outside the reference range. During a median follow-up of 45 months, 357 participants died. In unadjusted analysis, lower FT3 levels were associated with higher all-cause (HR per 0.1 pg/mL increase in FT3: 0.82 [95% confidence interval, 0.78–0.87]), cardiovascular (HR 0.74 [0.66–0.83]), cancer-related (HR 0.88 [0.80–0.97]) and other cause-related mortality (HR 0.83 [0.77–0.90]). After adjustment with Cox proportional hazard models, lower FT3 levels remained significantly associated with higher cardiovascular mortality (HR 0.83 [0.75–0.93]), but not with all-cause (HR 0.97 [0.92–1.02]), cancer-related (HR 1.02 [0.89–1.17]), or other cause-related mortality (HR 1.00 [0.92–1.10]). Lower levels of FT3 within the reference range may independently predict higher cardiovascular mortality in the general population. •Low FT3 within reference range is associated with higher cardiovascular mortality.•This association is independent of traditional cardiovascular risk factors.•This association remains significant after adjustment for TSH and FT4.•This association was consistent across subgroups of the population.