The primary disease of parathyroid glands is overactivity too much parathyroid hormone is produced. This is called hyperparathyroidism. Under this condition of hyperparathyroidism, one or more of the parathyroid glands behaves inappropriately by making excess hormone regardless of the level of calcium. In other words, the parathyroid glands continue to make large amounts of parathyroid hormone, even when the calcium level is normal and they should not be making hormone at all. Over-production of parathyroid hormone by overactive parathyroid glands (hyperparathyroidism) can rob you of your health, making you feel run down and tired, causing osteoporosis, and many other serious problems. Fortunately, hyperparathyroidism can be fixed with new minimally invasive surgery techniques in most people in under 20 minutes.
The most common cause of excess hormone production is the development of a benign (non-cancerous) tumor in one of the parathyroid glands. This enlargement of one parathyroid gland is called a parathyroid adenoma, and it accounts for 96% of all patients with primary hyperparathyroidism.
The most common situation is that one of the parathyroid glands has developed a tumor that is secreting all the hormone. The other 3 glands are small and are responding appropriately to the high calcium by becoming dormant.
This out of control parathyroid gland is rarely ever cancerous (less than one in 2,500); however, it slowly causes damage to the body because it induces an abnormally high level of calcium in the blood, which can slowly destroy a number of tissues. Parathyroid adenomas typically are much bigger than the normal pea-sized parathyroid and will frequently be about the size of a walnut.
Approximately 3% or 4% of all patients with primary hyperparathyroidism will have an enlargement of all 4 parathyroid glands, a term called parathyroid hyperplasia. In this instance, all of the parathyroid glands become enlarged and produce too much parathyroid hormone. This is a much less common scenario, but the end results on the tissues of the body are identical.
An even rarer situation occurs in less than 1% of the people who have 2 parathyroid adenomas while having 2 normal glands. This is very uncommon and can make the diagnosis and treatment of this disease a bit tricky.
Learn More about Hyperparathyroidism
Parathyroid Gland Basics
Normal and Abnormal Function of the Parathyroid Glands
Hyperparathyroidism Diagnosis and Treatments
How Many Parathyroids Are Affected?
A scientific study of 6,331 patients with primary hyperparathyroidism examined how many glands typically go bad in this disease. This study included data collected on a portion of patients with this disease over 10 years (1987-1997). The complete data and statistical analysis was published in March 1998 by Dr. James Norman's group in the Journal of the American College of Surgeons.
The results are as follows:
95.5% = one enlarged, overactive gland (termed a single adenoma)
4% = 4 enlarged, overactive glands (termed four-gland hyperplasia)
0.5% = 2 or 3 large glands (termed multiple adenomas)