Exploring the link between vitamin D and lipid profile in thyroid disorders: a comparative analysis of hypothyroidism, hyperthyroidism, and healthy control group

BACKGROUND: Thyroid disorders, including hyperthyroidism and hypothyroidism, are prevalent worldwide, affecting millions. Both thyroid hormone and vitamin D status regulate lipid metabolism, maintain cellular function via steroid receptors, and may influence each other's actions through similar gene response areas. AIM: This study aims to compare the lipid profile and vitamin D status levels in patients with thyroid disorders to those of healthy controls. MATERIALS AND METHODS: This cross-sectional, descriptive study included 225 individuals: 76 with hyperthyroidism, 75 with hypothyroidism, and 74 healthy controls. Blood serum samples were analyzed for concentrations of Thyroid-Stimulating Hormone (TSH), Free Triiodothyronine (FT3), Free Thyroxine (FT4), lipid profile, and 25-Hydroxyvitamin D (25(OH)D. RESULTS: Hypothyroidism patients exhibited significantly higher mean values of TSH (26.29±14.89 mU/L; p 0.001), BMI (24.16±3.62 kg/m2; p 0.001), total cholesterol (TC) (220.23±26.41 mg/dL; p 0.001), triglycerides (TG) (134.53±21.37 mg/dL; p 0.001), low-density lipoproteins (LDL) (144.6±25.53 mg/dL; p 0.001), very-low-density lipoproteins (VLDL) (26.90±4.27 mg/dL; p 0.001), and non-HDL cholesterol (157.50±29.63 mg/dL; p=0.032) compared to controls and hyperthyroidism patients. They also exhibited significantly lower mean levels of FT3 (0.535±0.71 ng/mL; p 0.001) and FT4 (10.95±6.41 pmol/L; p 0.001). Vitamin D levels were lower in hypothyroidism patients (25.30±13.69 ng/mL; p=0.035) compared to healthy controls (29.43±16.37 ng/mL) but higher than hyperthyroidism patients (23.02±15.55 ng/mL). A majority (60%) of hypothyroidism patients were vitamin D deficient (20 ng/mL; p 0.001).TSH showed a significant positive correlation with lipid parameters (p 0.05) except for High-Density Lipoprotein Cholesterol (HDL-C), which was inversely correlated. Vitamin D levels demonstrated a significant positive correlation with HDL-C across all groups (p 0.05). CONCLUSIONS: The study concludes that thyroid disorders are closely associated with vitamin D levels and lipid metabolism. There is a confirmed link between vitamin D, lipid profile, and cardiovascular risks in patients with thyroid disorders.