Patients with primary hyperparathyroidism (PHPT) show a high incidence of left ventricular hypertrophy, cardiac calcific deposits in the myocardium, and/or aortic and mitral valve calcification and thus may carry an increased risk of death from circulatory diseases. This prospective study was designed to assess an effect of parathyroidectomy on cardiac abnormalities of patients with PHPT. Echocardiography was used to evaluate the mechanical performance of the heart muscle, the thickness of the left ventricular wall, myocardial calcific deposits, and valvular calcifications within 12 and 41 months after parathyroidectomy. In a blinded fashion, aortic and mitral value calcifications were determined in 46% and 39% of patients with PHPT. Calcific deposits in the myocardium were found in 74% of patients. Follow-up studies after parathyroidectomy disclosed no evidence of progression of these calcifications. Before operation left ventricular hypertrophy was detected in 82%. After parathyroidectomy and 41 months of normocalcemia and normal PTH concentrations, a regression of hypertrophy of the interventricular septum and the posterior wall by -6% and -19% (P < 0.05) was observed. Subgroup analysis disclosed the most impressive long-term reduction of left ventricular hypertrophy in patients without a history of hypertension (-11% and -21%; P < 0.05 and P < 0.005); no changes were determined in 9 patients who developed secondary hyperparathyroidism after operation. The present data show a high incidence of left ventricular hypertrophy and aortic and/or mitral valve calcifications in patients with PHPT. Follow-up at 1 year and at 41 months after successful parathyroidectomy disclose regression of hypertrophy. Our results give evidence that parathyroid hormone per se plays an important role in the maintainance of myocardial hypertrophy. Post-surgical restoration of normocalcemia and normalization of parathyroid hormone valvular sclerosis persists without evidence of progression. We further conclude that patients with PHPT and parathyroidectomy are at low risk for the development of severe aortic and mitral valve stenosis within this period of time.