Serum ionized calcium and the prevalence of primary hyperparathyroidism in age cohorts of 75, 80 and 85 years.

In the elderly, primary hyperparathyroidism (HPT) is often disguised as 'senility' which can, however, be alleviated or cured by parathyroid surgery. The prevalence of HPT in the non-selected 75- to 85-year-old subjects (n = 610) randomly sampled from census records was estimated by measurements of serum ionized calcium and intact parathyrin levels. The prevalence of cases that require clinical attention seems to be around 3% in women and less than 1% in men. Furthermore, this study indicates that, on average, the serum ionized calcium concentration remains stable even in the elderly.