Role of thyroid disease in the development of statin-induced myopathy

Hypothyroidism is a common endocrine disease, which, in addition to its classic signs and symptoms, can present with primary complaints of myopathy. Myopathy can cause skeletal muscle weakness, tenderness, and pain and is often associated with elevated creatine kinase levels. There are many neuromuscular causes of myopathy, including inflammatory and infectious myopathies, metabolic and hereditary myopathies, and those caused by drugs or toxins. Hypothyroid patients with musculoskeletal symptoms can have elevated serum creatine kinase levels, which clinically resemble polymyositis. However, hypothyroid myopathies can be distinguished from polymyositis by coexisting signs and symptoms of hypothyroidism such as delayed relaxation phase of the deep tendon reflexes and the absence of inflammatory changes on muscle biopsy. The treatment of hypothyroidism with thyroid hormone replacement will alleviate symptoms of myopathy as well as lower the characteristic hyperlipidemia associated with hypothyroidism. Hypercholesterolemia, which can arise from different etiologies, is frequently treated with a class of HMG-CoA reductase inhibitors called statins. One of the most significant risks associated with the use of statins is the development of myopathy, a risk that may be compounded by the coexistence of hypothyroidism. The underlying metabolic mechanisms that account for muscle disease in these 2 settings show some common etiologies. The overlap of symptoms associated with hypothyroidism and statin-induced myopathy should prompt the physician to screen all patients presenting with myopathic symptoms with or without elevated creatine kinase levels and all hyperlipidemic patients before initiating statin therapy for hypothyroidism using a measurement of thyroid-stimulating hormone.