Atherogenic Index of Plasma as a Cardiovascular Risk Marker in Subclinical Hypothyroidism. A Comparative Study with Conventional Lipid Indices

Abstract

Background: Dyslipidemia, characterized by an imbalance in lipid profiles, is a recognized factor in the development of atherosclerosis and cardiovascular diseases. Current evidence suggests that non-traditional serum lipid ratios are more effective than traditional serum lipid parameters in predicting vascular diseases. Therefore, this study aims to investigate the relationship between atherogenic index of plasma (AIP; logarithm TG/HDL-c), Castelli risk index I and II (TG/HDL-c and LDL-c/HDL-c, respectively), and atherogenic coefficient (AC; non-HDL-c/HDL-c) using traditional serum lipid parameters (triglyceride (TG), total cholesterol (TC), LDL cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c)) with TSH in subclinical hypothyroidism. Material and Methods: The study was designed as a hospital-based cross-sectional observational study conducted for a period of four months from January–April 2026, in Central Clinical Laboratory and Department of Medicine of Adesh Institute of Medical Sciences and Research, Bathinda, a tertiary care teaching hospital in Punjab. A total of 200 subjects (100 cases and 100 controls) were enrolled in the study.Results: Lipid parameters including total cholesterol (p=0.001), triglycerides (p=0.001), HDL (p=0.049), LDL (p=0.001), and VLDL (p=0.001) were significantly higher in cases. Atherogenic indices such as AIP, Castelli Risk Index I, Castelli Risk Index II and AC were also significantly elevated (p<0.001), indicating increased cardiovascular risk among SCH patients. ROC curve analysis demonstrated that AIP showed the highest area under the curve (AUC=0.751), followed closely by CRI-I (AUC=0.748), CRI-II (AUC=0.744) and AC (AUC=0.656) while LDL cholesterol showed comparatively lower discriminatory ability (AUC=0.615). There was a significant difference (p=0.011) in area under curve for AIP and LDL when compared together.Conclusion: AIP correlated significantly (p=0.005) with serum TSH levels and showed a superior diagnostic performance (z=-2.542, p=0.011) (AUC for AIP=0.751) compared to LDL (AUC for LDL=0.651), suggesting that it may serve as a sensitive marker of cardiovascular risk in SCH patients as compared to traditional lipid markers.