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My doctors can't figure out what is going on with me. My calcium levels have been between 9.8 and 10.5 mg/dl over the last year. My PTH was 25 pg/ml. My Vitamin D was 89 ng/ml. I was diagnosed with a Vitamin D deficiency years ago so I have been taking 5000 units of Vitamin D daily since then. My doctor isn't sure if I have a parathyroid tumor or not. I've been feeling all of the symptoms of parathyroid disease and think this is what is wrong. What do you think?

Deva Boone
Answer authored by Deva Boone
Deva Boone, MD is the founder of the Southwest Parathyroid Center. As one of the most experienced parathyroid surgeons in the U.S., she has treated thousands of patients with parathyroid conditions.

This clinical picture looks typical for overuse of Vitamin D. One of the main roles for Vitamin D is to help your intestines absorb calcium. Vitamin D is a fat soluble vitamin, so it builds up in your body over time. You are currently on a very high dose of Vitamin D, which is why your Vitamin D level is high. Your lab might not label your Vitamin D as being in the “toxic” range, but it is high enough at 89 ng/ml (or 222 nmol/l) to cause high calcium levels. In cases like this, I often see the calcium fluctuate into the high range, with PTH levels staying in the low to low-normal range. 

At this point I could not definitively say whether you have a parathyroid tumor or not, because the Vitamin D complicates the picture. The first step is to stop taking Vitamin D and let the Vitamin D level drop. This can take months for it to drop back into a more normal range (under 50 ng/ml). Once it drops down to normal, your calcium level should also stabilize in the normal range. If your calcium remained high even with a normal Vitamin D, then that would indicate possible primary hyperparathyroidism. I usually have patients stop taking Vitamin D, then recheck labs (calcium, PTH, and Vitamin D) in 3 to 4 months. If the Vitamin D is still high, we may need to wait a few more months. Eventually, you will be able to tell whether the high calcium was due to the Vitamin D.

Vitamin D Diagnosis
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