Abstract: Objective To study the characteristics of hypothyroid myopathy in adults. Methods The clinical, biochemical, electromyographic, and pathologic characteristics of 19 patients with hypothyroid myopathy were analysed retrospectively. Results Proximal muscle weakness and elevation of muscle enzymes were the most common features. Other common clinical manifestations were myalgia, cramps, pseudomyotonia or stiffness after exercise. Muscular weakness with pseudohypertrophy was presented in some patients. Myoedema of temporal muscle was elicited by chewing continually. Hypothyroidism may be related to the pathogenesis of myasthenia gravis. Patients treated with levothyroxine achieved satisfactory outcomes. Hypothyroid myopathy is different from polymyositis in many aspects. Conclusion All patients presenting muscular weakness or elevation of muscle enzymes should be studied with their function of thyroid in order to avoid misdiagnosis.

Key words: hypothyroid myopathy, polymyositis, muscular hypertrophy, myasthenia gravis, diagnosis