LOS ANGELES, April 5 (UPI) -- For patients with hyperparathyroidism, a cause of osteoporosis, treatment with bisphosphonates increases the risk for bone fracture, rather than reducing it, according to a recent study.
Researchers at the University of California Los Angeles found patients with osteoporosis caused by the parathyroid condition were treated for more fractures if given drugs instead of surgery to remove the parathyroid or no treatment at all.
While most osteoporosis is caused by aging, an overactive parathyroid, which causes the release of too much of the hormone regulating calcium, also is a major cause.
The results were "startling," researchers said, because other indicators show the drugs help contribute to strengthening of bones, though with little data comparing the outcomes of surgery and drug treatment available before their study, they say they could not be sure.
"The drugs make the bones look dense on scans, but that is deceptive," Dr. Michael Yeh, an associate professor of surgery and medicine at UCLA, said in a press release. "We must presume there is a defect in the quality of the bone. But we don't know why."
For the study, published in the Annals of Internal Medicine, researchers analyzed medical data on 6,272 members of the Kaiser Permanente South California managed care system who were diagnosed with hyperparathyroidism between 1995 and 2010.
The researchers found there were 56 fractures per 1,000 people untreated for hyperparathryoidism 10 years after diagnosis, 20 fractures per 1,000 whose parathyroid had been removed surgically and 86 fractures per 1,000 patients treated with bisphosphonate drugs.
When including all types of bone fracture, the researchers found 206 fractures per 1,000 untreated patients, 157 fractures per 1,000 for those having surgery and 303 fractures per 1,000 when taking bisphosphonates.
The researchers said the fracture risk for people treated with the drugs was higher regardless of the type of osteoporosis they had.
While more research is needed to see if the drugs increase risk of fracture for people with other causes of osteoporosis, the researchers said at the very least their study suggests doctors consider options other than bisphosphonates for hyperparathyroidism patients.
"We were unable to demonstrate any benefit associated with this class of drugs, which have been around and routinely prescribed for more than 20 years," he said. "These findings should make bisphosphonates less attractive as an alternative to parathyroid surgery in patients with primary hyperparathyroidism."