Dyslipidemia in subclinical hypothyroidism and the effect of thyroxine on lipid profile

Subclinical hypothyroidism (SH) has a prevalence between 4% and 10.5% in various studies. The burden of SH in India is expected to increase with increasing iodine sufficiency. Studies have shown conflicting results concerning not only the degree of lipid changes in SH but also the effect of thyroxine substitution therapy. Indian studies on dyslipidemia in SH and the effect of thyroxine on lipid profile are currently lacking.

(1) To assess the association of SH and lipid profile. (2) To quantify the effect of thyroxine treatment on lipid profile.

About 54 patients who were detected to have SH were compared with 56 healthy controls. Thyroid stimulating hormone (TSH), free T3, free T4, anti thyroperoxidase (TPO) antibodies, total cholesterol, high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, Very low density lipoprotein (VLDL) cholesterol, serum triglycerides were measured in all the patients after an overnight fast. Selected patients were started on thyroxine replacement. Twenty-one patients were followed up after 3 months with a repeat lipid profile.

Mean total cholesterol and mean LDL levels were significantly higher in SH compared to controls, but there was no statistically significant difference in the mean HDL, VLDL, and triglyceride levels. There was a significant reduction in mean T. cholesterol, mean LDL, mean VLDL, and mean triglyceride levels after treatment with thyroxine, while there was no significant difference among the mean HDL levels.

Dyslipidemia is more common in SH compared to controls. There is a TSH dependent increase in cholesterol, LDL, VLDL, and triglyceride levels. Achieving euthyroid status with thyroxine has a favourable effect on lipid profile.