You probably know that the old XLH treatment, among its many side effects, tended to cause hyperparathyroidism (overactive parathyroid glands). Some XLHers, me included, can develop hyperparathyroidism even without any treatment! Back before I had even heard the term XLH, when I was in my twenties, a random blood panel revealed high parathyroid hormone (PTH) levels, but the doctor didn’t have a clue about why, and we never followed up on it, attributing it to a lab error. Now, in retrospect, I know the results were correct and the elevation was due to my XLH.
My parathyroids settled down over time without any treatment and were fine until about twenty years ago, when I did start phosphorus/calcitriol treatment, and even though I was on a tiny dose (too small to actually do anything), my PTH rose. I went on cinacalcet for a while, and it was fine for a year or two, but then it stopped working, and at the time, the best thing seemed to be to simply stop the phosphorus/calcitriol that triggered the problem and wasn’t doing me any good anyway! My PTH levels promptly normalized again.
But now they’re rising fast, and have been for the last two or three years. They were fine during the first seven or eight years on burosumab, so I don’t think that’s the trigger, but they’ve gotten to not just a high level, but a scary-high level, and I’m exhausted all the time. So I’m back on cinacalcet. (I also slightly reduced the burosumab before starting the cinacalcet. The PTH didn’t drop, and in fact continued to rise, after I reduced the burosumab.) I haven’t had labs done since starting the cinacalcet, so I don’t know if it’s working. I’m still tired, but it’s hard to tell if that’s due to the high PTH or just, yanno, my getting old.
I expect my insurance company will balk in a few months, because cinacalcet is expensive. Not in the same league as burosumab, but still expensive and in the non-XLH context is generally only used for a relatively short period of time, so the cost will stand out as something unusual. I expect the insurance company will push for me to have some portion of the parathyroid glands removed, since over the long term, the surgery will be less expensive than years of cinacalcet. I was actually surprised that my endocrinologist didn’t recommend going straight to surgery, since I’d already tried cinacalcet unsuccessfully. Apparently it’s not uncommon for us to need to increase the dosage over time, which the previous doctor (with less XLH expertise) never tried, and may not be required in other settings where cinacalcet is prescribed.
There doesn’t seem to be a real consensus on how to deal with a burosumab patient who has elevated PTH, once it gets above the acceptably high range (as mine has). The main options, as best I can tell—not a doctor, remember—are: 1) add cinacalcet, or 2) remove all/part of the parathyroids. I suppose it’s possible that stopping burosumab completely might help, but I’m not willing to try that option!
Neither of these options is great. As noted, my previous experience with cinacalcet wasn’t successful, and the insurance company may be a problem. Surgery is risky, first because all surgery is risky, and beyond that, the parathyroids are so incredibly tiny that there are horror stories galore of surgeons failing to find them or removing other necessary bits instead. And since the underlying cause of the overactivity isn’t being corrected (whatever it is in our metabolism that makes the parathyroids think that normal levels of phosphorus are too high), there’s a significant risk that any parathyroid bits that remain (often it’s a partial removal, not a complete removal) will simply regrow over time. And if they’re removed in their entirety, then patients need to take yet another pill to replace the natural parathyroid hormone that we still need.
On the plus side, I’m fortunate to have access to really top-notch medical specialists, including a whole department at Brigham & Women’s that does nothing but thyroid and parathyroid surgery! So if I do need surgery, I’ll be confident that the surgeon knows how to find the parathyroid glands!
I’ll let you know how the journey goes. There isn’t much information available, especially from the patient’s perspective, about hyperparathyroidism in XLH, so I hope you’ll find it interesting. And if you have experience that you’re willing to share, good or bad, I’d love to hear it!
***
Please note that the author is a well-read patient, not a doctor, and is not offering medical or legal advice.
If you’d prefer to read this blog as a newsletter, sent straight to your inbox, please sign up here.