The authors describe a case of hypothyroidism the only symptom of which at presentation was myopathy. Hypothyroidism was diagnosed only after abnormalities of thyroid hormones, thyroid scanning, and antithyroglobulin and antimicrosome antibodies were found. The authors conclude that the diagnosis of hypothyroidism is very difficult in the absence of the typical signs, such as drowsiness, edema, dry skin, hoarse voice, alopecia, etc.