Prevalence of hypercalcaemia in a health survey: a 14-year follow-up study of serum calcium values.

Among 16,401 subjects attending two health screenings, in 1969 and 1971, 176 showed hypercalcaemia on both occasions, i.e. serum calcium values above 2.60 mmol l-1. The prevalence of hypercalcaemia increased in women with advancing age and occurred in close to 3% of those above the age of 60, whilst in men it was found in less than 0.7% in all age groups. The mean serum calcium concentration in women above the age of 50 was significantly higher than in men. This observation could at least partly explain why hyperparathyroidism (HPT) is more often diagnosed in females. Only nine persons were initially referred for neck exploration. Most of the others were not even notified of the biochemical disturbance and thus it was possible to study the serum calcium values in an unattended cohort until follow-up after 14 years. In the hypercalcaemic patients there was little or no increase in serum calcium during these years. In no patient did the serum calcium level rise above 3.0 mmol l-1. Altogether, 24 patients from the initial cohort were subsequently operated on for primary HPT but there were only two further cases of verified HPT, which developed during the follow-up period, in those who had been clearly normocalcaemic at the health surveys. In conclusion, hypercalcaemia, presumably caused by primary HPT, is common but apparently develops slowly and with little risk of a progressive rise of serum calcium concentrations.