Doc: Vitamin D deficit after gastric bypass takes time to normalize
Dear Dr. Roach: I am a 72-year-old woman in fair health. I had strong bones until I had gastric bypass surgery. Within two years, I developed osteoporosis. In 2016 my parathyroid hormone level was found to be elevated. However, it has come down over the past year or two from 97.76 to 68.95 pg/mL. The endocrinologist now has me on 8,000 IU of vitamin D-3 per day. My calcium was 9.3 and ionized calcium was 5.0.
Meanwhile, the rheumatologist treating my osteoporosis has prescribed Reclast infusions once per year. I just received my second one this month.
This summer I broke a toe on my right foot with no known trauma. In October I sustained a stress fracture of my left heel bone, again without any known trauma. I am very worried about what all this means to my future bone health.
Dear L.MJ.: I suspect you had vitamin D deficiency due to the gastric bypass surgery, which prevents your body from absorbing it efficiently. Without vitamin D, your bones cannot take up calcium as effectively. The parathyroid hormone often will increase in this situation, and this is called "secondary hyperparathyroidism."
It's important to note that both your total and ionized calcium levels are normal. Ionized calcium is the active form -- some calcium binds to albumin, a major protein in blood. In secondary hyperparathyroidism, the calcium is never high. A high calcium and high parathyroid level always means primary hyperparathyroidism, which almost always comes from a tumor of the parathyroid gland. Unfortunately, I have seen people whose doctors have confused this point and missed the diagnosis.
With replacement of your vitamin D (at a high-enough dose, you can absorb enough), the PTH level is settling back down to normal, and it would be expected that your bone strength would start going up as well. I would expect your endocrinologist or rheumatologist to follow your bone density through a DEXA scan.
The Reclast (zoledronic acid) is an intravenous bisphosphonate, and it slows down reabsorption of your bone. Between the higher vitamin D and the Reclast, your bones should get better and your risk of fracture will decrease, but it will take time.
Dear Dr. Roach: I know several people who donate plasma and get paid for it. Is it wearing on your body to donate often?
Dear I.E.: Essentially nobody in the U.S. is paid for donating blood now. Blood banks are concerned, with some evidence, that people who donate for pay are more likely to have communicable diseases, especially viruses, in their blood. Even though blood is extensively tested, not paying for blood is one additional way of keeping the blood supply safe. However, studies have shown that giving other kinds of gifts to blood donors — shirts, coupons, etc. — does not increase the risk of unsafe donation.
Plasma donation differs from blood donation in that the blood cells are returned to the donor, and it's the proteins and fluid that are taken and used. These are then purified and processed to kill any virus or bacteria that might have been in the donor's blood. The infection risk from plasma-derived transfusions is essentially nil.
The body has a harder time replenishing blood cells than blood proteins. The Food and Drug Administration allows plasma donations twice weekly, though the American Red Cross only allows every 28 days.
Readers may email questions to ToYourGoodHealth@med.cornell.edu