Unusually high calcium levels in the blood can almost always be traced to primary hyperparathyroidism, an undertreated, underreported condition that affects mainly women and the elderly, according to a new study by UCLA researchers.
The condition, which results from overactive parathyroid glands and includes symptoms of bone loss, depression and fatigue that may go undetected for years, is most often seen in African American women over the age of 50, the researchers discovered.
The study, currently online in the Journal of Clinical Endocrinology and Metabolism, is one of the first to examine a large, racially and ethnically diverse population — in this case, one that was 65 percent non-white. Previous studies had focused on smaller, primarily Caucasian populations.
The four parathyroid glands, which are located in the neck, next to the thyroid, regulate the body's calcium levels. When one is dysfunctional, it can cause major imbalances — for example, by releasing calcium from the bones and into the bloodstream. Over time, calcium loss from bones often leads to osteoporosis and fractures, and excessive calcium levels in the blood can cause kidney stones and worsening kidney function.
The UCLA researchers determined that hyperparathyroidism is the leading cause of high blood-calcium levels and is responsible for nearly 90 percent of all cases.
"The findings suggest that hyperparathyroidism is the predominant cause of high calcium levels, so if patients find they have high calcium, they should also have their parathyroid hormone level checked," said the study's lead author, Dr. Michael W. Yeh, an associate professor of surgery and endocrinology at the David Geffen School of Medicine at UCLA.
Hyperparathyroidism, which affects approximately 1 percent of the population, can be detected by measuring parathyroid hormone levels to determine if they are elevated or abnormal.
For the study, researchers utilized a patient database from Kaiser Permanente Southern California that included information on 3.5 million individuals, a population roughly the size of Ohio. Using data from lab results, the research team identified 15,234 cases of chronic high-calcium levels. Of those cases, 13,327 patients (87 percent) were found to have hyperparathyroidism.
The incidence of hyperparathyroidism — reported as the number of cases per 100,000 people per year — was found to be highest among African Americans (92 women and 46 men), followed by Caucasians (81 women and 29 men), Asians (52 women, 28 men) and Hispanics (49 women and 17 men).
The research team also found that with advancing age, the incidence of hyperparathyroidism (per 100,000 people per year) increased and that more women were affected:
•Under age 50: 12 to 24 cases for both genders
•Ages 50-59: 80 women and 36 men
•Ages 70-79: 196 women and 95 men
"It was surprising to find the highest incidence in black women over age 50," Yeh said. "We had traditionally thought of the disorder as affecting mostly Caucasian women."