Thyroid Hormones Linked to Type 2 Diabetes Prevalence

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Levels of thyroid hormones may be associated with prevalence of type 2 diabetes.
Levels of thyroid hormones may be associated with prevalence of type 2 diabetes.

There appears to be a correlation between thyroid hormones and prevalence of type 2 diabetes in both men and women, according to results from a cross-sectional study published in the Journal of Clinical Endocrinology & Metabolism.

“This paper is the first report showing that serum thyroid hormones and thyroid-stimulating hormone concentrations are related to the prevalence of type 2 diabetes mellitus in the general population,” Yeqing Gu, from the Nutritional Epidemiology Institute and School of Public Health at Tianjin Medical University, and colleagues wrote.

The researchers evaluated 15,296 patients from Tianjin, China, where prevalence of type 2 diabetes was 16.2% (1449 of 8970) in men (1449 of 8970 patients; mean age: 48.1 years) and 7.7% women (488 of 6229 patients; mean age: 47.6 years). The researchers measured the relationships between type 2 diabetes and serum free FT3, free FT4, FT3/FT4 ratios, and thyroid-stimulating hormone (TSH) levels in both men and women.

Patients were divided into 5 quintiles based on concentrations of FT3, FT4, and TSH. Men had a FT3 concentration ranging from 3.50 pmol/L to 6.50 pmol/L, a FT4 concentration from 11.50 pmol/L to 22.69 pmol/L, and TSH concentration ranging from 0.55 mIU/L to 4.78 mIU/L. For women, concentrations of FT3 and TSH were the same as men, with FT4 concentrations ranged between 11.50 pmol/L and 22.46 pmol/L.

“Decreased FT3, FT3/FT4 ratios, and increased FT4 levels were independently related to the prevalence of [type 2 diabetes] among the adult population,” Gu and colleagues wrote. “Significantly negative relationship between TSH and [type 2 diabetes] was observed in males, but not in females.”

The adjusted odds ratios (ORs) for developing type 2 diabetes for men in the higher quintiles of FT3 levels vs patients in the lowest quintile in each of the quintiles were 0.75 (95% CI, 0.63-0.89), 0.70 (95% CI, 0.58-0.84) 0.63 (95% CI, 0.52-0.76) and 0.56 (95% CI, 0.46-0.68). For FT4, the ORs for the higher quintiles vs the lowest were 1.05 (95% CI, 0.87-1.27), 1.16 (95% CI, 0.96-1.40), 1.09 (95% CI, 0.90-1.31), 1.29 (95% CI, 1.07 – 1.56). For the higher quintiles of FT3/FT4 ratios vs the lowest, odds ratios were 0.69 (95% CI, 0.58-0.83), 0.72 (95% CI, 0.60-0.86) 0.59 (95% CI, 0.48-0.71), and 0.55 (95% CI, 0.46-0.66).

In women adjusted ORs between type 2 diabetes for higher quintiles of FT3, FT4, FT3/FT4 ratios, and TSH vs the lowest were 0.97 (95% CI, 0.72- 1.30), 0.91 (95% CI, 0.67-1.22), 0.71 (95% CI, 0.52-0.96), and 0.63 (95% CI, 0.46-0.86). For FT4, the ORs for higher quintiles vs the lowest were 0.81 (95% CI, 0.58-1.13), 1.15 (95% CI, 0.84-1.58), 1.12 (95% CI, 0.81-1.54), and 1.54 (95% CI, 1.14-2.08). For FT3/FT4 ratios for higher quintiles vs the lowest, the ORs were 0.79 (95% CI, 0.59-1.05), 0.56 (95% CI, 0.41-0.76), 0.64 (95% CI, 0.47-0.85), and 0.57 (95% CI, 0.42-0.78). For TSH for higher quintiles vs the lowest, the ORs were 1.22 (95% CI, 0.91-1.66), 0.83 (95% CI, 0.601.15), 0.89 (95% CI, 0.65-1.22), and 0.82 (95% CI, 0.60-1.12).

Gu and colleagues noted that study limitations include its cross-sectional nature, thereby causality cannot be inferred, and the fact that only 1 serum thyroid hormone test and TSH test was conducted in a healthy population of patients with thyroid hormone levels in the euthyroid range. They explained that further cohort and intervention trials, and high-quality research were needed, respectively, to confirm the results.

“[A]lthough the participants with thyroid disease were excluded, serum thyroperoxidase antibodies levels were not routinely checked in the general population,” Gu and colleagues said. “Therefore, we cannot fully exclude the possibility that the relationship between the categories of [thyroid hormones], TSH, and [type 2 diabetes] is affected by these patients with positive thyroperoxidase antibodies.”

Disclosures: The researchers report no conflicts of interest.

Reference

  1. Gu Y, Li H, Bao X, et al. The relationship between thyroid function and the prevalence of type 2 diabetes mellitus in euthyroid subjects [published online December 1, 2016]. J Clin Endocrinol Metab. doi:10.1210/jc.2016-2965.
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