The following is a summary of “Thyroid Hormones and Diabetes in Euthyroid Hispanic/Latino Adults of Diverse Backgrounds: HCHS/SOL,” published in the June 2024 issue of Endocrinology by Persky, et al.
Previous studies have highlighted connections between endogenous thyroid hormones and diabetes, but questions remained regarding the specific stages of diabetes development influenced by these hormones, the mechanisms involved, and the role of the hypothalamic-pituitary-thyroid axis. For a study, researchers sought to investigate the relationships between thyroid hormones and incident prediabetes and diabetes, as well as changes in glycemic traits, in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), the largest cohort of Hispanic/Latino adults in the United States with diverse backgrounds.
The study cohort consisted of 592 postmenopausal euthyroid women and 868 euthyroid men aged 45 to 74 years without diabetes at baseline from the HCHS/SOL. Baseline thyroid hormones included thyrotropin (TSH), free thyroxine (FT4), total triiodothyronine (T3), and derived indices assessing pituitary sensitivity to thyroid hormone. Transitions to diabetes and prediabetes and changes in glycemic traits measured at the 6-year follow-up were analyzed using multivariable Poisson and linear regressions.
Among women, T3 (incident rate ratio [IRR] = 1.65; 95% CI, 1.22-2.24; P = .001) and TSH (IRR = 2.09; 95% CI, 1.01-4.33; P = .047) showed positive associations, while FT4 (IRR = 0.59; 95% CI, 0.39-0.88; P = .011) exhibited an inverse association with the transition from prediabetes to diabetes. In men, the T3/FT4 ratio was positively associated with transitioning from normoglycemia to prediabetes but not from prediabetes to diabetes. Indices reflecting pituitary sensitivity to thyroid hormone suggested increased sensitivity in men transitioning from prediabetes to diabetes.
The study findings suggested that in women, there are positive associations of T3 and TSH and inverse associations of FT4 with transitioning from prediabetes to diabetes, indicating reduced pituitary sensitivity to thyroid hormones. In men, inverse associations of thyroid indices with transitioning from prediabetes to diabetes, but not from normoglycemia to diabetes, suggested increased pituitary sensitivity to thyroid hormones later in diabetes development.