Primary hyperparathyroidism (PHPT) is a condition that is most common in postmenopausal women, occurring in about 1 in 250 women between 50 and 60 years old. PHPT occurs when the tiny parathyroid glands on the back of the thyroids produce too much parathyroid hormone, often as a result of a tumor.

PHPT leads to high levels of calcium (hypercalcemia) in the blood, which is linked to osteoporosis and kidney problems such as kidney stones and kidney failure. It is also associated with an increased risk for certain cancers, including breast, colon, and prostate cancer. PHPT can also affect the nervous system, making people depressed and tired.

It did not take a lot of calcium to reduce the risk of a parathyroid tumor.

Researchers had believed that PHPT had something to do with a person’s calcium intake and calcium metabolism over many years. Since women have more of a problem with calcium loss as evidenced by their increased rates of osteoporosis, researchers in a recent study used data from the long-term Nurse’s Health Study to examine the association between calcium intake and in the risk of PHPT in women.

The investigators followed 58,354 women between 39 and 66 years old in 1986 with no history of PHPT who were participating in the Nurses’ Health Study I. Calcium intake (from both diet and supplements) was assessed every four years using food frequency questionnaires over a 22-year period.

Women were divided into five equal groups, based on their dietary calcium intake. The women in the group with the highest intake of dietary calcium had a 44 percent reduced risk of developing PHPT compared with the group with the lowest intake.

Even women who took 500 mg/day of calcium, a relatively modest amount, had a 59 percent lower risk of developing PHPT than those taking no calcium supplements. James Norman, chief of surgery at the Norman Parathyroid Center and who wrote an editorial published with the study, told TheDoctor it was interesting that it did not take a lot of calcium to reduce the risk of a parathyroid tumor.

The study found that women who just got calcium via diet alone, and did not take any supplements, had the highest rate of parathyroid tumor development as they got older. Taking calcium supplements above the normal dietary intake through a vitamin, reduced the likelihood that tumors would form and lead to PHPT.

“Although this study does not prove what causes the parathyroid tumor, it does show a nice association between supplemental calcium and a decreased incidence of tumor development,” said Norman. The theory is that when women don’t take enough calcium, their parathyroid glands have to overwork and they are more likely to develop a tumor.

The study is published online in the British Medical Journal.