Comment on A. Ghemigian, et al. Familial isolated primary hyperparathyroidism due to HRPT2 mutation.

I would like to comment that parathyroid scanning is performed with a lipophilic cationic complex of Tc, called sestamibi, and not free technetium pertechnetate, as is described in the article. According to the guidelines, dual phase Tc-sestamibi scans are commonly used for preoperative localization of parathyroid adenomas. Hyperactive parathyroid cells have a high concentration of sestamibi and accumulate more radiopharmaceutical, visualized in early images, 10-15 min post injection. Parathyroid adenomas usually show slower washout compared to normal thyroid gland, visualized as retention of sestamibi in delayed images, 2h p.i. (possibly due to mitochondrial binding or reduced PgP expression). However, some lesions (10%-15%) will show washout of tracer by 2h that is as fast as that from the thyroid. Many hyperplastic glands show such a rapid washout. Washout of tracer from adenomas is variable. Besides, some thyroid nodules could also accumulate and retain sestamibi. This is why dual phase sestamibi scintigraphy is often combined with thyroid scan (which is performed with free Tcpertechnetate) for differential diagnosis, especially in the case of hyperfunctioning parathyroid tissue very close to the thyroid gland or intrathyroidal adenoma. The distributions of the two tracers can be visually compared and, afterwards, the thyroid scan can be digitally subtracted from the parathyroid scan to remove the thyroid activity and enhance the visualization of parathyroid tissue. Comparison of the two scans with image subtraction procedures may increase the study sensitivity.