Thyroid function regulates a wide array of metabolic parameters. Thyroid function significantly affects lipoprotein metabolism as well as some cardiovascular disease (CVD) risk factors, thus influencing overall CDV risk. Decrease in muscle creatine in hypothyroidism may also contribute to thyroid myopathy. True myopathy is a primary muscle involvement characterized by slowed muscle contraction and relaxation, muscle pain, proximal muscle weakness, sluggish ankle jerks and absence of sensory involvement. Pain on muscle exertion is due to defective carbohydrate metabolism. The present study was designed to evaluate creatine kinase and lactate dehydrogenase activity in thyroid disorders and control subjects.