Wednesday, April 16, 2014

An Interesting Case of Hypocalcemia

I saw this patient for the first time last month. Young guy, who was found on routine exam to have marked hypercalcemia of 12.1. His parathyroid hormone was high as well.
Pretty slam-dunk case of hyperparathyroidism, and given his young age, extent of hypercalcemia, surgery is clearly indicated, so I sent him for parathyroid localization via sestamibi scanning, followed by a surgical consult.
The surgeon agreed, and he proceeded to have minimally-invasive parathyroidectomy. His intra-op PTH did drop by 70%, thus with biochemical cure, the surgeon closed him up. His postop Ca was normal so he was discharged home.
A week later, his PCP calls me; he presented with tingling, numbness and cramps- was then found to have hypocalcemia this time. His Ca was 7.1, with normal albumin levels.
Uh-oh. At this point, the index of suspicion should be high for hypoparathyroidism, which is not uncommon after neck surgery, often transient, even if the remaining parathyroids were left alone.Treatment in these cases should include Calcium supplementation, along with activated Vitamin D.
One should order a parathyroid hormone level to see if this is inappropriately low, which would confirm the diagnosis. Also, a Magnesium should be checked in case he had hypomagnesemia, which induces a state of PTH resistance.
His PTH came back 80 (normal 15-65). To my surprise.
Diagnosis?
"Hungry Bone" Syndrome. 
Haven't seen one of these since fellowship. Since osteoclastic and osteoblastic activity are coupled, after removal of the parathyroid adenoma, the osteoclasts suddenly slow down, leaving the still-busy osteoblasts to take up too much of the serum calcium to lay down new bone, causing the hypocalcemia. Treatment: high dose Calcium and Vitamin D. Should be self limited.

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