Echocardiography detected pericardial effusions in five out of six consecutive untreated patients with severe primary hypothyroidism and suspected myopathy, whereas the chest X-ray suggested only one. During L-thyroxine replacement, serial echocardiograms detected decrease in the size of the effusions in all the patients. This occurred before the serum thyroid stimulating hormone (TSH) levels had significantly changed, although there was a small but significant rise in serum thyroxine. In one patient complete resolution of the effusion occurred before the patient became euthyroid, a previously unreported finding.
Small voltage complexes, T-wave inversion and non-specific T-wave flattening were the commonest electrocardiographic abnormalities noted. The former invariably and the latter two abnormalities frequently, reverted to normal before the patient became biochemically and clinically euthyroid. T-wave inversion in a particular lead, however, did not invariably do so, suggesting that permanent structural change might possibly have occurred.
The plasma creatine kinase (CK) was raised in four patients, and markedly raised at levels usually associated with muscular dystrophy, in two. At the onset of resolution of the pericardial effusions, the total plasma CK had fallen significantly in all patients in whom it was raised.