Parathyroid hyperplasia may be missed by double-phase Tc-99m sestamibi scintigraphy alone.

The authors report two cases of parathyroid imaging with double-phase Tc-99m sestamibi used in conjunction with Tc-99m pertechnetate that detected parathyroid hyperplasia when the wash out rate of MIBI from the glands paralleled normal thyroid tissue. Routine use of thyroid images for comparison may avoid this pitfall. The authors also observed that Tc-99m sestamibi has early uptake in brown tumors.