The effects of parathyroidectomy on left ventricular muscle volume and mechanical performance were evaluated echocardiographically in 24 patients with secondary hyperparathyroidism due to chronic renal failure and in 7 with primary hyperparathyroidism. Intraventricular septum and posterior wall thickness, left ventricular end-diastolic diameters, shortening fraction, ejection fraction, and left ventricular mass index were measured by M mode recording by the parasternal short axis view prior to parathyroidectomy as baseline and repeated 12 months after parathyroidectomy. Serum basal carboxyterminal parathyroid hormone levels in patients with secondary hyperparathyroidism (34.4 +/- 13.7 ng/ml) were significantly higher than in those with primary hyperparathyroidism (3.4 +/- 5.1 ng/ml; p < 0.0001). At 12 months after parathyroidectomy, intraventricular septum and posterior wall thickness, left ventricular end-diastolic diameter and left ventricular mass index were reduced from 11.8 +/- 3.1 mm, 10.9 +/- 1.7 mm, 53.8 +/- 6.3 mm, 200.8 +/- 57.1 g/m2 to 10.0 +/- 2.1 mm (p < 0.05), 9.8 +/- 1.9 mm (p < 0.05), 50.7 +/- 7.2 mm (p < 0.05), 149.6 +/- 38.7 g/m2 (p < 0.0001), in patients with secondary hyperparathyroidism. In patients with primary hyperparathyroidism, all echocardiographic parameters remained in the normal range and did not show any significant changes before or after parathyroidectomy. From this study, parathyroid hormone at extremely high concentrations as seen in secondary hyperparathyroidism appears to be a cardiotoxic substance. Therefore, all patients with secondary hyperthyroidism should be examined by echocardiography and parathyroidectomy should be considered if myocardial hypertrophy is present.