A new drug can help control an overactive thyroid, a major complication of advanced kidney disease, by playing a trick on the gland, a new study finds.
The drug, cinacalet, is much more effective at keeping the parathyroid gland working normally than a placebo, according to the study. It may be a good alternative to standard therapy, researchers said.
Your kidneys clear waste products from your body. But when the kidneys do not work properly, a buildup of waste can occur and hemodialysis may be needed to filter the blood.
Hemodialysis is, literally, "cleaning the blood." In this procedure, the patient is hooked up to a dialysis machine, which acts like an artificial kidney and circulates blood through a filter that cleans it. Patients on dialysis need to repeat this procedure often to keep waste products from building up in the body.
One of the complications of chronic kidney disease is hyperparathyroidism, where too much parathyroid hormone is produced. The parathyroid glands are located in the neck and control calcium and phosphorus metabolism.
When these glands are overactive, there are significant problems with bone, blood vessels, and other tissues. When the level of parathyroid hormone is too high, the bones lose calcium and phosphorus. Bones become thin and painful and fracture easily.
In addition, the calcium and phosphorus that come from the bones can be deposited in the heart and blood vessels, causing cardiovascular problems.
"Part of the treatment in chronic kidney disease is finding ways to control hyperparathyroidism," said researcher Dr. Kevin J. Martin, a professor of internal medicine and director of nephrology at Saint Louis University.
The current treatment involves using large doses of vitamin D and calcium to keep blood levels of calcium and phosphorus normal, he noted. However, "while these measures are effective, they are not uniformly effective," Martin said.
"In this study we show a new way to try to control the parathyroid glands using a novel drug, which fools the parathyroid gland into thinking that blood calcium is high and shutting down the secretion of parathyroid hormone," he said.
Martin's team randomly assigned hemodialysis patients who received standard treatment but still had hyperparathyroidism to cinacalcet or to a dummy drug. Cinacalcet was given to 371 patients, and 370 patients received the dummy drug.
Over 26 weeks, 43 percent of those receiving cinacalcet had normal parathyroid hormone levels compared to 5 percent of the patients receiving the dummy drug.
In addition, the amount of calcium and phosphorus in the blood dropped 43 percent among those receiving cinacalcet, but showed an increase of 9 percent among those taking the dummy drug, according to the report in the April 8 issue of the New England Journal of Medicine.
Based on these results, Martin said that "this is a way to control overactive parathyroid glands in a large proportion of patients that can't be controlled by standard therapy."
"Cinacalcet gives us another tool to try to control hyperparathyroidism," he said.
But the problem needs to be controlled with multiple approaches tailored to each patient. These include vitamin D and calcium supplements, and now cinacalcet, Martin said. "If we can control hyperparathyroidism better it will be translated into better patient outcomes."
Dr. Gary Curhan, associate professor of medicine at Harvard Medical School, said that controlling hyperparathyroidism has always been a huge challenge, and this new medication provides the opportunity to study whether reducing the parathyroid hormone level is beneficial.
"But as studies of other conditions have shown, what we think is best isn't always best," he added.
Curhan, the author of an editorial in the same journal issue, said more studies are needed to see if there are long-term benefits or reductions in bone disease, fractures, and cardiovascular disease that can be attributed to the drug.