Possible Normocalcemic Hyperparathyroidism


Question

I have a 57 year old female with an elevated intact PTH. Initally the PTH was in the 200 range associated with nml calcium , phosphorous a n d cr but with a decreased vit D-OH. We then replaced vit d with 50000 u D2. Now 6 to 7 months later her calcium is nml @9.3 mg/dl; phos= 4.4 mg/dl; Vit d-25 total is 144 ng ml (vit D-25-OH-D2) and creatinine is slightly elevated at 1.11 mg/ dl but her PTH intact is staying in the 68 to 109.4 pg/ml at last check with the afore mentioned labs ....why? Dr. Mary Lynn Kemick , mskemick@lexhealth.org

Response

This sounds like a case of normocalcemic primary hyperparathyroidism. These patients are characterized by a persistently normal serum calcium but an elevated PTH. In your patient, the vitamin D deficiency could have been responsible for the elevated PTH, but with replacement, the PTH continues to be elevated. This rules out a secondary hyperparathyroidism due to vitamin D deficiency. It is remotely possible that the creatinine of 1.1 mg/dL could reflect a creatinine clearance that is diminished, but I would doubt it would be in the range (i.e. <40 cc/min) that could explain an elevation of PTH to this magnitude. The entity, 'normocalcemic primary hyperparathyroidism' is being seen with increasing frequency, but guidelines as to how to manage these patients are not clear. The upcoming report of the International Workshop on the management of asymptomatic primary hyperparthyroidism (J Clin Endocrinol & Metab, February, 2009) will give you more information on this variant of primary hyperparathyroidism.John Bilezikian , MD