Cores in hypothyroid myopathy: a clinical, histological and immunofluorescence study

Fifteen patients with primary hypothyroidism were evaluated neurologically. Needle biopsies of skeletal muscle were obtained using a Bergstrom needle. In 73% of the patients, cores were identified histologically and by electr on microscopy in the skeletal muscle of these patients. The presence of cor es correlated with the severity of hypothyroidism, muscle hypertrophy, cram ps and the duration of the hypothyroid state. There was no significant corr elation with muscle weakness. Immunofluorescence studies with N-CAM antibod ies demonstrated staining of the sarcolemma, cytoplasm and central regions (cores) in the hypothyroid muscle, These imply that the presence of cores i n hypothyroid myopathy is due to reactivation of embryonic proteins that di srupt skeletal muscle architecture. (C) 2000 Elsevier Science B.V. All righ ts reserved.