Figure 1b. Parathyroid imaging in MEN 1: US and computed tomography (CT). (a) Parathyroid adenoma. US image of the neck demonstrates the typical appearance of a parathyroid adenoma in MEN 1: a well-defined, oval hypoechoic mass posterior to the thyroid gland. (b) Parathyroid adenoma in a different patient. Contrast material–enhanced CT scan of the neck shows a right inferior parathyroid adenoma (arrow).