Hypothyroidism presenting as hypercholesterolaemia and simvastatin-induced myositis

We report on a 50-year-old woman who presented with hypertension. She was given simvastatin for hypercholesterolaemia. The creatine kinase level was 3180 U/L at the 3-month follow-up visit, which was thought to be due to simvastatin treatment. Although treatment was discontinued, the creatine kinase level 4 months later remained higher than 3000 U/L. Echocardiography revealed mild pericardial effusion and normal left ventricular function; the electromyogram was also normal. The patient subsequently showed signs and symptoms suggestive of hypothyroidism, which was confirmed by measurements of the concentration of thyroid-stimulating hormone (>100 mU/L) and free thyroxine (<2 pmol/L). Thyroxine replacement therapy normalised the creatine kinase and cholesterol levels. This case illustrates the importance of excluding underlying causes of hypercholesterolaemia before contemplating lipid-lowering therapy.