 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 . 
