Abstract Background Primary hyperparathyroidism (pHPT) is associated with increased morbidity and mortality rates, especially due to cardiovascular disease. This may be an effect of metabolic alterations in lipoprotein, glucose and urate turnover. The few previous reports studying this matter have been inconclusive and have included only hypercalcaemic patients. Methods In a population-based screening of 5202 postmenopausal women, 109 were diagnosed with mild pHPT. Some 92 patients, together with matched controls, were investigated to analyse metabolic disturbances, and the effect of parathyroidectomy and hormone replacement therapy (HRT). Sixty-nine pairs completed the 5-year study. Results Patients had higher serum calcium and parathyroid hormone levels than controls. They had hypertriglyceridaemia and a significantly increased amount of triglyceride-rich lipoproteins. Furthermore, patients had pronounced hypercholesterolaemia, although the level of high-density lipoprotein–cholesterol was lower, and higher serum blood glucose and urate levels. While 5 years of surveillance only failed to affect these alterations, parathyroidectomy with or without addition of HRT normalized the metabolic changes. Thus, 4 years after surgery no differences were seen between cases and controls. Conclusion The metabolic alterations in mild pHPT span over many extraparathyroid metabolic systems and constitute an increased risk of cardiovascular disease and death. Parathyroidectomy has a reversing effect on these proatherosclerotic changes, while surveillance does not affect the outcome. Even in mild pHPT surveillance may be questioned.