Frequency and characteristics of lingual thyroid not detected by screening.

Four patients with lingual thyroid glands presenting beyond the neonatal period have been evaluated at the Hospital for Sick Children, Toronto since the advent of neonatal TSH screening. All were female, clinically euthyroid at diagnosis and presented with symptoms of a lingual mass. We estimate that 1.6% of lingual thyroids are missed by this TSH based thyroid screening program and approximately 1/600,000 live births present in childhood or adolescence with a lingual thyroid. Physicians should still include lingual thyroid in the differential diagnosis of a mass at the base of the tongue.