Primary hyperparathyroidism can be caused by a benign tumor, multiple benign tumors, or hyperplasia (all four parathyroid glands diseased). The symptoms are all the same. With an adenoma, or tumor, there is one diseased parathyroid and the other three glands are all normal. Sometimes you can have multiple adenomas, with two or even three benign tumors and one normal gland. In hyperplasia, all four parathyroid glands are diseased. There are technically no normal glands, though usually there will be one or two glands that are closer to normal in size and appearance than the others. Having more glands involved does not mean that you have more symptoms, or less. The symptoms are exactly the same.

Most of the time, we won’t know that hyperplasia is present until the operation, when all four glands are found to be diseased. In this case, we have to remove 3 and a half glands, leaving part of the most normal-appearing parathyroid behind. The end result is the same, and the relief in symptoms is the same as you would expect after removal of an adenoma.