I prefer to evaluate all four parathyroid glands rather than rely on intraoperative PTH. Here is why: intraoperative PTH is just not that accurate. Here is the thinking behind ioPTH: a surgeon can remove one parathyroid, often one seen on preoperative imaging, test the PTH level in the blood, then wait 5 to 10 minutes and test again, then wait 5 or 10 more minutes and test again. If the PTH drops to normal range, and/or by 50%, the surgeon can stop the operation without looking at the other parathyroids.   Unfortunately, if you remove a parathyroid tumor, it is very likely that the PTH will drop by 50%, and into normal range, even if there is another parathyroid tumor. The drop indicates that you removed a parathyroid tumor, but in many cases does not tell you anything about the remaining glands. I know this from experience - this was how I was trained to do the operation in fellowship. It seemed unreliable at the time, but it was the best thing we had. Once I was experienced enough to reliably find all four parathyroid glands, I realized this was a much better method. I have performed many reoperations (patients who were not cured the first time and need a second operation) on patients who had had a one-gland operation somewhere else, and had a PTH drop of 50%, into normal range - and still had the disease.

Another problem with intraoperative PTH, which is perhaps worse, is that sometimes people take a little longer to have a PTH drop, even if they are actually cured. If the PTH doesn’t drop, the surgeon then starts digging around for the other parathyroids. Unfortunately, since the surgeon does not routinely look for all four glands, there is a pretty good chance that he will inadvertently injure the glands, and a very good chance that he won’t find them all. He may also then injure surrounding structures like the nerve that controls the voice. For these reasons, I would discourage any surgeon who does not routinely look at all four parathyroid glands from doing so based on a PTH level.

I would actually prefer that surgeons not check PTH in the OR at all. If it drops, you can’t guarantee that the person is cured. If it doesn’t drop, you can’t guarantee that there is another tumor, and you may do more harm than good by digging around randomly.

Although I don’t check intraoperative PTH, I do check PTH about an hour after the person gets to the recovery room (after looking or trying to look at all four parathyroid glands). At this point, the PTH is a lot more accurate. But I don’t want to see a 50% drop, or a PTH in the normal range. I want to see a suppressed PTH - that is, a PTH below normal range. After an hour, most people will have had enough time for the PTH to drop. And it should not drop to normal range if you have a high calcium level. Remember that high calcium levels will suppress normal parathyroid glands, so the normal glands should not be making much PTH. The PTH should thus be in the low range, not normal range.