Effects of thyroxine replacement on lipid profile and endothelial function after thyroidectomy

Hypothyroidism is a risk factor for atherosclerotic cardiovascular disease. This study investigated the effects of L-thyroxine replacement therapy on lipid profile and endothelial function after thyroidectomy in patients with overt transient non-autoimmune hypothyroidism.

Twenty-two patients with non-toxic multinodular goitre treated by total or near-total thyroidectomy and 22 healthy individuals matched for age, sex and body mass index were studied. Lipid profile and endothelial function were determined in each patient at the euthyroid phase before thyroidectomy (stage 1), the hypothyroid phase 3 weeks after surgery (stage 2), and the euthyroid phase 3 months (stage 3) and 6 months (stage 4) after the start of thyroxine treatment.

The lipid profile and endothelial function deteriorated between stage 1 and stages 2 and 3. Findings at stage 4 were similar to those at stage 1. There was a positive correlation between serum thyroid-stimulating hormone (TSH) and total cholesterol (r(s) = 0.588, P < 0.001), and a negative correlation between serum TSH and flow-mediated arterial dilatation (r(s) = 0.506, P < 0.001). Total cholesterol and TSH were independent determinants of endothelial function.

A 3-week hypothyroid period after thyroidectomy led to a more atherogenic lipid profile and impaired endothelial function that persisted for at least 3 months.