Age- and sex-related incidence of surgically treated primary hyperparathyroidism

Background Primary hyperparathyroidism (1 degrees HPT) is reported most often in women over the age of 50. Beyond that, little is known about the epidemiology of this condition, and no studies have specifically examined the age and gender distribution of patients with 1 degrees HPT. Methods We analyzed patients from the Nationwide Inpatient Sample (NIS), a 20% random sample of all hospital stays from 2000-2004, and also from the University of Michigan endocrine surgery database from 1999-2005. Surgically treated 1 degrees HPT was used as a surrogate marker for 1 degrees HPT. An age- and sex-based frequency distribution was computed for each dataset. Results A total of 7,513 females and 2,677 males who underwent surgery for 1 degrees HPT in the 5-year period 2000 through 2004 were reported in the NIS. At the University of Michigan from 1999 through 2005, 790 females and 276 males underwent parathyroidectomy for 1 degrees HPT. In both datasets, the frequency of 1 degrees HPT began to rise slowly in both sexes at age 11 and increased more rapidly among females than males beginning at age 21-25 (NIS) and 26-30 (UM). Incidence curves for both women and men in both databases were similar in shape and unipolar in configuration. Peak incidence was at age 56-60 (NIS) and 61-65 (UM) in females and age 56-60 in males (both datasets). The female:male ratio was noted to rise steadily among the NIS patients until perimenopausal age, after which it became stable for the next 20 years before decreasing again. No change in the female:male ratio over time was seen among the UM patients. Conclusions Primary HPT occurs more frequently in females than in males at all ages. The incidence increases steadily after age 25 in both sexes. The female:male ratio does not change during the peri- and postmenopausal years. This information should stimulate new hypotheses to explain the difference in the incidence of 1 degrees HPT between men and women.