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Hyperthyroxinemia is positively associated with prevalent and incident type 2 diabetes mellitus in two population-based samples from Northeast Germany and Denmark

Ittermann T, Schipf S, Dörr M, Thuesen BH, Jørgensen T, Völzke H, Markus MRP

Nutrition, metabolism, and cardiovascular diseases : NMCD, 2018

6,784 participants

Abstract

BACKGROUND AND AIMS: A potential causal relationship between thyroid function and type 2 diabetes mellitus is currently under debate, but the current state of research is limited. Our aim was to investigate the association of thyroid hormone levels with prevalent and incident type 2 diabetes mellitus (T2DM) in two representative studies.

METHODS AND RESULTS: Analyses are based on data from the Study of Health in Pomerania (SHIP), a German population based cohort with 4308 individuals at baseline and 3300 individuals at a five-year follow-up, and from INTER99, a Danish population-based randomized controlled trial with 6784 individuals at baseline and 4516 individuals at the five-year-follow-up. Serum thyroid-stimulating hormone (TSH) and free thyroxine (fT4) concentrations were measured in both studies, while free triiodothyronine was measured in SHIP only. T2DM was defined by self report or intake of anti-diabetic medication. Neither in SHIP nor in INTER99 we detected significant associations of serum TSH levels with prevalent or incident T2DM. Serum fT4 levels were significantly positively associated with prevalent T2DM in SHIP and INTER99. In longitudinal analyses baseline levels of fT4 were significantly positively associated with incident T2DM in SHIP (RR per pmol/L = 1.07; 95%-CI = 1.05-1.10), while this association barely missed statistical significance in INTER99 (RR per pmol/L = 1.03; 95%-CI = 0.99-1.06). In SHIP baseline fT3 levels were significantly associated with…

How strong is the evidence?

Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 6,784 participants or records.

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