Preliminary data are available on the coexistence of primary hyperparathyroidism and breast carcinoma. To further understand the association between hyperparathyroidism and breast cancer, we conducted a record-linkage study in Sweden using the Swedish Cancer Registry from 1958-1997. A total of 9,835 women who underwent surgery for primary parathyroid adenoma were followed to evaluate the hypothesis that a history of primary hyperparathyroidism increases the risk of subsequent breast cancer. During 99,929 person-years of follow-up, 331 cases of newly diagnosed breast cancer were reported. The number of expected breast cancers in this population was 260.0. This resulted in a standardized incidence ratio of 1.27 (95% confidence interval [CI] = 1.14-1.41). The relation persisted over time after the surgical removal of the parathyroid adenoma. Possible explanations for the observed association are a shared etiology including genetic and environmental factors such as early life radiation, and hypercalcemia after the overproduction of parathyroid hormone, which may increase breast cancer incidence.
Copyright 2004 Wiley-Liss, Inc.