Type III hyperlipidaemia with primary hypothyroidism: a unique clinical course of hyperlipidaemia during replacement...

A patient is described with type III hyperlipidaemia and primary hypothyroidism who had a unique clinical course of hyperlipidaemia. The patient was a 65-year-old man with primary hypothyroidism. His plasma total cholesterol, triglyceride and high density lipoprotein-cholesterol concentrations 1 year after starting thyroid hormone replacement therapy were 7.98, 4.04 and 0.72 mmol/l, respectively. His plasma apolipoprotein (apo) E level was 0.29 g/l and its phenotype was E2/2. Remarkably, this patient had no hyperlipidaemia before starting thyroid hormone replacement therapy but it became overt only after the hypothyroidism had been treated. Although we have not confirmed the mechanism for this, we speculate that a decrease in enzyme activities responsible for cholesterol production may have been sufficient to surpass the effect of apolipoprotein E2/2 and the decrease in enzyme activities involved in degrading and excreting plasma cholesterol, resulting in normolipidaemia.