Hi, Dr Boone, Thanks so much for accepting questions! I found you through Lani Simpson's Master Class. My PTH has been between 24 and 44, calcium between 9.1 and 9.5, phosphorus between 3.9 and 4.3 and vitamin D between 47 and 64 over the last 4 years (I've been on vitamin D supps for at least 2 decades). I could dig up numbers from the years before, but I don't think there was ever much difference. Reason I'm asking is that I lost 19% of my forearm bone density over the course of those 4 years (11% at spine, and 1.5% at hip). No gastric bypass, I'm an omnivore, no diarrhea. Kidney function normal. I take only 40mg calcium in the form of bone meal. The reason I take so little is that 2-3 years ago, when I did a 24h urine calcium test while taking 400mg calcium supp a day and DIDN'T stop taking it when doing the test, I was at 301 (whatever the unit is). Then I repeated that test 2 months later, and didn't take any calcium supp, and the result was 205. Both my doctors told me it was unnecessary to take calcium supps in that case. I "compromised" and kept taking 40mg. I just want to cover my bases by making sure whether or not I'm losing so much bone because of my parathyroid, since this affects any kind of treatment plan.
Hi, thanks for writing in! If you are in Lani’s group then you are in good hands.
Parathyroid disease often causes bone loss, and the most severe bone loss in parathyroid disease is often seen in the forearm. That is, when someone with parathyroid disease gets osteoporosis, we often see the worst numbers in the forearm, or radius, as opposed to the femur or lumbar spine. So when someone has significant loss in the forearm and not in other areas, it is reasonable to consider parathyroid disease as a cause.
We diagnose parathyroid disease based on labs. Your calcium, PTH, and Vitamin D levels are all consistently in the normal range, so we can rule out primary hyperparathyroidism as the cause of your osteoporosis. Your calcium level tends to be a little on the lower side, but this may be normal for you, especially since your PTH levels indicate that your parathyroids are “happy” with those calcium levels. (If you had a calcium of 9.1 mg/dl and a PTH of 70 pg/ml, I would say that your parathyroid glands were not happy with the calcium of 9.1 and were trying to get the calcium up by making more hormone. But this is not the case here.)
Urine calcium is not the most reliable test, but since your urinary calcium was not super low when you were off calcium, you could argue that extra calcium supplementation is not necessary (because it suggests that you are probably getting enough through your diet). Since urinary calcium is not that reliable, though, I tend to not base a lot of decisions around it, unless the results are really abnormal. As far as whether to take calcium supplements or not, that is up to you. Your labs do not indicate secondary hyperparathyroidism (which would warrant calcium supplementation), so if you are getting enough calcium in your diet then extra calcium may not be necessary.