Impact of Vitamin D Supplementation on Lipid Profile and Vascular Stiffness in Patients with Hypothyroidism: A Prospective Randomized Controlled Study

Abstract

Background: Hypothyroidism has been connected with dyslipidemia and elevated cardiovascular risk through underlying metabolic abnormalities and impairment of function of the endothelium. In this context, vitamin D insufficiency is common and linked to with adverse cardiometabolic profiles, but its therapeutic effects remain contested. Aim of Study: The aim of this research was to evaluate how vitamin D supplementation affected the lipid profiles and vascular stiffness in hypothyroidism. Materials and Methods: This is an interventional prospective randomized controlled clinical trial (RCT) enrolled 120 adults with primary hypothyroidism who were allocated in a 1:1 ratio to either the vitamin D supplementation group (G1, n = 60) or the control group (G2, n = 60). A computer-generated random sequence was used to allocate groups. Participants in the intervention group received standard levothyroxine therapy plus oral cholecalciferol (2,000 IU/day) for six months, whereas those in the control group received standard levothyroxine therapy alone. Clinical, biochemical, lipid profile, and vascular stiffness assessments, including augmentation index (AIx) and pulse wave velocity (PWV), were performed at baseline before initiation of treatment and repeated after the 6-month intervention period. Treatment effects were evaluated using both within-group and between-group comparisons, and effect sizes (Cohen's d) with corresponding 95% confidence intervals (CIs) were calculated to quantify the magnitude of observed differences. Results: Vitamin D treatment significantly improved the lipid parameters and vascular stiffness versus controls Conclusion. Total cholesterol and LDL-C declined by −26.2 mg/dL (95% ) and −24.2 mg/dL (95% ), respectively, and triglycerides by −23.1 mg/dL (95% CI: −28.5 to −17.6; β = 0.85) and HDL-C increased by +3.5 mg/dL (95% ). Results showed reductions in PWV (−1.3 m/s [95% ]) and AIx (−4.8% [95% ]). The control group is non-demonstrates any marked changes. Lower levels of LDL-C, PWV, and AIx were linked to higher serum 25(OH)D levels (all p < 0.01). Conclusion: In individuals with hypothyroidism, vitamin D treatment improved arterial stiffness and lipid profiles. Nevertheless, because of the limited sample size, short follow-up, and absence of objective clinical results, the results do not permit causal inference and probably generalizability. These results both replicated some prior evidence and failed to reconcile important inconsistencies between studies. These associations need to be validated in larger well-powered randomized trials with prolonged follow-up and mechanistic end points.