Ectopic lingual thyroid gland is an uncommon abnormality of migration of the thyroid gland. Although it is uncommon, it is often found in the region of the foramen cecum as a lingual thyroid at the base of the tongue in patients whose gland fails to descend. The true incidence of lingual thyroid is unknown. Treatment depends on the presence of symptoms. In this case report, we described a 17-year-old man who presented with growth retardation due to severe hypothyroidism associated with a lingual thyroid gland. He did not complain of pressure symptoms. We recommended regular follow-up visits to monitor this state of thyroid function and the size and shape of the gland. We wanted to note that ectopic thyroid tissue should be taken into consideration in the differential diagnosis of all lingual and pharyngeal masses, and in the differential diagnosis of hypothyroidism.