Long-term hypoparathyroidism tied to calcium deposits in breasts

Women with hypoparathyroidism persisting beyond one year after surgery to remove the thyroid have more calcium deposits in their breast arteries, which may indicate a higher risk for cardiovascular disease, according to a study from Turkey.

However, because no cardiovascular data were available, these calcifications should be viewed “as a potential imaging marker that requires validation — rather than an established risk tool,” the researchers wrote. The study, “Breast arterial calcification in women with permanent postoperative hypoparathyroidism: a case-control study,” was published in BMC Endocrine Disorders.

Hypoparathyroidism is caused by abnormally low levels of parathyroid hormone (PTH), which is normally produced by the parathyroid glands in the neck. PTH helps control levels of calcium and phosphorus in the body. Over time, its lack can cause calcium to build up in the body’s organs and form deposits called calcifications.

Long-term hypoparathyroidism often occurs following a surgical procedure, and is often defined as permanent when it persists beyond one year. Although calcifications can build up in multiple organs in permanent hypoparathyroidism, “to our knowledge, no previous study has specifically focused on breast calcifications,” the researchers wrote.

Their study focused on breast arterial calcifications, which are deposits in the walls of arteries, the blood vessels that supply blood to the breast. It involved 80 women who had their thyroids surgically removed. The parathyroid glands are located just behind the thyroid and may accidentally be damaged or removed during surgery.

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Forty women developed permanent hypoparathyroidism after surgery. The other 40 women had also had thyroid surgery but did not develop hypoparathyroidism and were used as a control group. The two groups were similar in age and time since surgery, with complete removal of the thyroid, known as total thyroidectomy, being the most common surgical procedure (72.5% vs. 62.5%).

As expected, hypoparathyroidism treatment differed between the two groups. Almost all women with permanent hypoparathyroidism (95%) received calcitriol, an active form of vitamin D, compared with none in the control group. The use of levothyroxine, which replaces the natural thyroid hormone after surgery, was similar in both groups (97.5% vs. 92.5%).

Blood tests showed that women with permanent hypoparathyroidism had lower levels of circulating calcium. They also had more than four times lower levels of PTH than women in the control group. Their estimated glomerular filtration rate (eGFR), a measure of kidney function, was also lower, suggesting greater kidney damage.

The researchers reviewed their mammograms (X-ray images of the breasts), looking for different types of calcification. The mammograms showed no difference in parenchymal calcifications (deposits within breast tissue) or ductal calcifications (deposits in the milk ducts). Breast density, which describes how much fibrous and glandular tissue is present compared with fatty tissue, was also similar.

However, breast arterial calcifications were significantly more common in women with permanent hypoparathyroidism (30% vs. 7.5%), who were more than five times as likely to have this type of calcification as women in the control group. On average, they also had higher BAC scores, a measure that combines the number, length, and severity of the calcified blood vessels.

The BAC scores increased with age and were associated with lower circulating calcium and PTH levels and lower eGFR. However, when the researchers considered some measurements — such as calcium and supplement doses — as potential consequences of hypoparathyroidism, age remained independently linked to BAC scores, but calcium and PTH were not.

The presence of breast arterial calcification is “an established marker of cardiovascular risk in the general population,” so its assessment on routine mammography may also represent “a potential imaging marker of cardiovascular risk in this population,” the researchers wrote. However, the findings need to be confirmed in larger studies that follow patients over time, they said.