Tc-99m pertechnetate thyroid images in hyperthyroidism. Size, distribution, and presence of a pyramidal lobe.

One hundred consecutive thyroid images obtained by use of Tc-99m pertechnetate, in authenticated cases of hyperthyroidism, were reviewed. Calibrated images showed that only 42 of the 200 thyroid lobes (21%) were greater than 5 cm in length. The enlarged lobes occurred in 29 patients. Of these, only 4 had a multinodular appearance (and 7 patients with smaller lobes also had multinodular glands). Neither thyromegaly (by length) nor multinodular appearance are common features of hyperthyroidism in this area. There were 12 instances of pyramidal lobes in the hyperthyroid men (12 of 26 = 46%) and 24 cases in women (24 of 74 = 32%). The site of origin of the pyramidal lobe was from the left in 17, from right in 16, and from the midline in 3 cases. During the period of review of all thyroid images, only one other case of a pyramidal lobe was found (a case of multinodular goiter).