The mediators and predictors of higher values of thyroid-stimulating hormone in type 2 diabetes mellitus: a cross-sectional study

Marwan Salih Al-Nimer; Randa Majeed Salih

Marwan Salih Al-Nimer Department of Clinical Pharmacology and Therapeutics, College of Medicine, University of Diyala, Baqubah, Iraq
Randa Majeed Salih Department of Anesthesiology, Ishtar Medical Institute, Baghdad, Iraq

Keywords: type 2 diabetes mellitus, thyroid-stimulating hormone, mediation effect, predictors, triglyceride-glucose index, interleukin-6

Abstract

Subclinical hypothyroidism associated with a higher level of thyroid-stimulating hormone (TSH) is commonly reported in type 2 diabetes mellitus (T2DM). Multiple causes, rather than a specific cause, have been reported for this association. This study aims to investigate some biomarkers as mediators or predictors of the higher levels of TSH in T2DM. This cross-sectional study included 150 diabetic patients. The patients were grouped according to their TSH levels into Group I (0–4 μIU), Group II (4.1–8.0 μIU), and Group III (>8.0 μIU). Anthropometric measurements, glycemic and lipid indices, thyroid hormones, and inflammatory biomarkers (including C-reactive protein and interleukin 6) were determined. The mediation (indirect effect) was assessed using the Sobel test, and prediction was evaluated using logistic regression and Receiver Operating Characteristic tests. Groups II and III showed significantly higher values of these biomarkers. None of these biomarkers has an indirect (mediation) effect on the high levels of TSH. Duration of the disease, triglyceride-glucose index, interleukin-6, and stress hyperglycemia ratio are significant predictors. These predictors have areas under the curves of 0.810, 0.805, 0.869, and 0.562, respectively. We conclude that specific biomarkers can predict higher TSH levels, but they do not act as mediators.