September 10, 1996
Media Contact: John Cramer
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An apparently harmless mutation in a gene that helps control the level of calcium in the blood eventually may be used to identify people with an increased risk of osteoporosis and other hormone-related bone diseases, a Johns Hopkins study suggests.
Results of the study, which was supported by the National Institutes of Health, will be presented Sept. 10 at the annual meeting of the American Society for Bone and Mineral Research in Seattle.
Researchers tested the DNA in blood samples from 27 people with primary hyperparathyroidism and 71 healthy people and discovered a mutation in the gene that helps regulate calcium and thereby bone density and mass. Results showed that the mutation in the calcium-sensing receptor gene was not linked with an increased risk of primary hyperparathyroidism.
However, the mutation may have a role in osteoporosis, one of the most common bone diseases, and other bone diseases that occur when the body's calcium level is too high or too low, says Michael Levine, M.D., the study's senior author and a professor of medicine.
"Although the mutation itself does not directly cause a depletion or overabundance of calcium in the blood, its presence may be evidence of a more serious mutation in the same gene," says Levine.
This gene regulates calcium-sensing receptors on the surface of cells in the parathyroid gland. The gland produces parathyroid hormone, which helps control the calcium level in the blood. The mutation, or slight change in DNA base pairs, does not alter the structure of the protein manufactured by the gene. But it may alter the protein's ability to work, thereby interfering with production of parathyroid hormone.
The Hopkins scientists plan to begin a large screening program to determine the mutation's possible role in osteoporosis. Early identification and treatment of osteoporosis may reduce or prevent bone thinning.
The parathyroid glands are two pair of small glands in the neck alongside the thyroid gland. Hyperparathyroidism, or overproduction of parathyroid hormone, causes thinning of the bones, depression and other problems. Hypoparathyroidism, or underproduction of parathyroid hormone, interferes with muscles and nerves, causing painful spasms or seizures.