Parathyroid hyperplasia in primary hyperparathyroidism can be tricky. Adenomas are straightforward: one “bad” gland is removed, and the normal ones are left behind. With hyperplasia, all four glands are involved, by definition. There are no completely normal glands. This is why we have to remove 3.5 glands, to debulk the parathyroids. In most cases, this produces a long-term cure. Meaning, that little piece works fine, and even though it isn’t completely normal, it is small enough that it never causes problems. We intentionally choose the most normal-looking gland to leave behind. If that gland has been relatively spared, and hasn’t grown as large as the other glands, then there is a good chance it won’t ever get like the others. The chance that you would ever need another parathyroid operation is low - I would expect it to be the same as others undergoing surgery for primary hyperparathyroidism, so closer to 1%.

With the things you have been reading, I’m wondering if some of them are talking about parathyroid hyperplasia caused by SECONDARY hyperparathyroidism. In this case, there is another cause for the parathyroid overgrowth. Cutting out some parathyroid glands can help, but unless the underlying condition is treated (like kidney failure, for example), the hyperplasia will return, and a second operation may be necessary. In cases of secondary hyperparathyroidism, you always see hyperplasia (all four glands involved). In cases of primary hyperparathyroidism, you occasionally see hyperplasia. But online, a lot of the articles on hyperplasia will be talking about secondary hyperparathyroidism.