 The hospitalization rate for hyperparathyroidism in the United States in 1999 was 8.0 out of 100,000. The disease has a definite tendency to affect younger individuals, typically appearing before the age of 40, with a study in 1922 reporting that 70 % of cases display symptoms before the age of 20, and 85 % before 35. Primary hyperparathyoidism, as well as OFC, is more common in Asiatic countries. Before treatment for hyperparathyroidism improved in the 1950s, half of those diagnosed with hyperparathyroidism saw it progress into OFC.
