Primary congenital hypothyroidism is a heterogeneous disorder caused by dyshormonogenesis, ectopia of the gland, or athyrosis.1 The differentiation between these underlying abnormalities is based primarily on the results of thyroid scintigraphy. Iodide is concentrated by the thyroid gland and organified to form iodine. This trapping of iodide, or of technetium-99m pertechnetate (99mTc), is the physiologic foundation of thyroid scintigraphy. The mechanism for iodide transport against a concentration gradient, the iodide pump, is shared by the thyroid, salivary glands (SGs), and the gastric mucosa.2 Thus, SGs and the stomach are normally visualized on thyroid scanning.
Recently, we noted an absence of SG activity on the99mTc images in an infant with congenital hypothyroidism. To determine the frequency of this finding in the various subsets of infants with congenital hypothyroidism, we retrospectively reviewed the thyroid scans of infants with this disorder seen in our institution.