When one or more of your parathyroid glands become abnormal it is called hyperparathyroidism. In this situation your gland (or glands) make too much (“hyper”) parathyroid hormone. Too much hormone raises the blood calcium to unsafe levels.
High blood calcium causes many symptoms and problems for your body. Instead of stopping the rising calcium like it should, the parathyroid gland only makes it go higher. This problem occurs because one (more rarely 2,3 or 4) of the parathyroid glands stops working with the rest of the body. It develops a growth (also called an adenoma) and swells to a larger size. It no longer senses calcium levels in the blood and instead of listening to what the body needs, just keeps raising the calcium level. Like a “runaway train” the calcium level gets higher and higher and the symptoms and problems you experience get worse and worse. 97% of the time only one of the glands is the culprit. It develops a benign growth called a parathyroid adenoma.
Less commonly (2-2.5% of the time), a person will develop enlargement of all four glands. This is not an adenoma, but is called hyperplasia. Even more rare is a condition where an individual will develop enlargement of just two glands, which is called “multiple adenomas”. And finally, much less than 1% of the time, a malignant growth may be found in the abnormal parathyroid.
Again, by far the most common situation is one in which only one of the glands becomes abnormally large and it is not a cancer. It is important to emphasize that cancer of the parathyroid is extremely rare compared to other cancers with which the reader may be familiar. The important thing to know is that the majority of people only have one enlarged gland. This can be surgically removed successfully and with minimally invasive techniques as the next sections will explain further.