Relationship Between Thyroid Dysfunction and Diabetes

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by insulin resistance and impaired insulin secretion, resulting in persistent hyperglycemia. ( )..In T2DM, the response to insulin is diminished, and this is defined as insulin resistance. During this state, insulin is ineffective and is initially countered by an increase in insulin production to maintain glucose homeostasis, but over time, insulin production decreases, resulting in T2DM.( ).

Glycemic parameters are critical indicators for diagnosing and monitoring diabetes mellitus. The most commonly used measures include fasting blood glucose (FBG), postprandial blood glucose (PPBG), and glycated hemoglobin (HbA1c). Among them, HbA1c reflects the average blood glucose levels over the previous two to three months and is considered a reliable marker of chronic hyperglycemia.( ) Diabetic dyslipidemia constitutes a distinct cluster of plasma lipid and lipoprotein abnormalities that are metabolically interconnected in individuals with type 2 diabetes mellitus. This condition is predominantly characterized by elevated triglyceride (TG) concentrations, reduced levels of high-density lipoprotein cholesterol (HDL-C) ( ).

The underlying mechanism involves insulin resistance, which disrupts normal lipid metabolism by enhancing hepatic very low-density lipoprotein (VLDL) synthesis and impairing the clearance of triglyceride-rich lipoproteins. ( ) Prevalence of thyroid dysfunction is greater in diabetes patients compared to the general population.1-3 Prevalence of thyroid dysfunction in general population is around 6.6-13.4%, while in diabetes population around 10-24%.1 Studies found that subclinical hypothyroidism is the most common thyroid dysfunction in diabetic population ( ) Emerging evidence suggests a complex interplay between glycemic control, lipid metabolism, and thyroid function in patients with type 2 diabetes mellitus. Poor glycemic control has been associated with adverse lipid profiles and alterations in thyroid hormone levels, which may collectively contribute to the progression of diabetic complications. Thyroid hormones influence both glucose and lipid metabolism by regulating hepatic glucose production, lipolysis, and insulin sensitivity. ( ).

This study was conducted in Upper Egypt, a region characterized by distinct sociodemographic and health profiles compared to other parts of the country. Despite the growing burden of non-communicable diseases, including type 2 diabetes, there is a noticeable lack of regional epidemiological data addressing the coexistence of metabolic syndrome and thyroid dysfunction. Investigating this relationship in the Upper Egypt population may help fill existing knowledge gaps and support the development of more effective, geographically tailored healthcare strategies.

Inclusion criteria

• Patients diagnosed with type 2 diabetes mellitus in upper egypt.
• Age above 18 years.
• Patients who gave informed consent to participate.

Exclusion criteria

• Patients with type 1 diabetes mellitus.
• Age below 18 years.
• Patients with known autoimmune thyroid diseases, pregnancy, or acute illness at the time of assessment.