Biochemical Signatures of Hypothyroidism: Comparative and Correlation Analyses in Overt and Subclinical Subtype

Abstract

Background: Hypothyroidism, characterized by insufficient production of thyroxine (T4) and triiodothyronine (T3), is associated with systemic metabolic and renal alterations. While levothyroxine is standard therapy, persistent metabolic disturbances are frequently observed, and data from the Indian population are limited.

Objective: To evaluate metabolic and renal parameters in overt and subclinical hypothyroid patients and examine correlations with thyroid hormones.

Methods: In this hospital-based retrospective study (January 2023–December 2024), 532 adults were included: 276 hypothyroid patients and 256 age- and sex-matched controls. Hypothyroid patients were classified as overt hypothyroidism (OH, n = 43) or subclinical hypothyroidism (SCH, n = 233). Assessments included thyroid function (fT3, fT4, TSH), glucose metabolism (FBS, HbA1c), lipid profile (TC, LDL, HDL, TGL, VLDL), and renal function (serum urea, creatinine). Group comparisons and correlation analyses were performed.

Results: Hypothyroid patients exhibited higher total cholesterol, triglycerides, fasting glucose, HbA1c, serum urea, and creatinine compared with controls, reflecting a pro-atherogenic, insulin-resistant profile with mild renal impairment. Positive correlations were observed between TSH and lipid/glucose markers. Even SCH patients demonstrated measurable biochemical alterations. Micronutrient status (iodine, selenium, vitamin D) was not assessed, which may influence outcomes.

Conclusion: Hypothyroidism in this cohort is associated with dyslipidemia, impaired glucose metabolism, and mild renal dysfunction. Elevated TSH correlates with adverse metabolic markers, highlighting the systemic impact of thyroid dysfunction. Comprehensive metabolic and renal monitoring is recommended to optimize risk stratification and guide management beyond thyroid hormone replacement.