Turkish Journal of Endocrinology and Metabolism, (2006) 2 : 49-52 49 CASE REPORT Correspondence address: Şenay Arıkan Dicle University, Medical School Department of Endocrinology, Diyarbakır, Turkey Tel : 0412 248 80 01 Fax : 09 248 85 20 E-mail : sarikan@dicle.edu.tr An Embryological Cause of Primer Hypothyroidism, Lingual Thyroid Şenay Arıkan* Deniz Gökalp* Alpaslan Tuzcu* Mithat Bahceci* Selen Bahceci** Dicle University, Medical School, Diyarbakır, Turkey * Department of Endocrinology ** Department of Histology and Embryology Lingual thyroid is a rare developmental thyroid abnormality usually affecting females. It is often found in the region of the foramen caecum as a lingual thyroid at the base of the tongue in patients whose gland fails to descend. A 16-year-old female patient with severe hypothyroidism applied to our outpateint clinic. She was complaining from growth retardation, primary amenorrhea, weakness, decreases of school performance and short stature. No thyroid tissue was seen at the usual site with ultrasonography. Scintigrapy with 99mTC pertechnetate showed an ectopic functioning thyroid in the lingual area. CT scan showed a mass in the base of lingular region. The thyroid profile implied severe hypothroidism (free T3:0,142 ng/dl, free T4:0,741 ng/dl, and TSH:100 µIU/ml). Patient was accepted as primary hypothyrodism due to ectopic thyroid tissue (lingual thyroid) and substitution treatment with L- thyroxine was started at the dose of 2-3 µgr/kg. Surgical treatment did not consider because of patient was asymptomatic in terms of pressure. As a result we reported a rare cause of primary hypothyroidism due to ectopic thyroid gland (lingual) in a young female patient. Keywords: Lingual thyroid, juvenile hypothyroidism, ectopic thyroid Introduction Ectopic lingual thyroid gland is uncommon developmental abnormality. Abnormality of the embryological development and migration of the thyroid gland can result in ectopic thyroid tissue. Ectopic thyroid tissue may be found anywhere along the embryologic "path of descent" of the thyroid gland between the foramen caecum and the anterior mediastenium. Although uncommon, it is often found in the region of the foramen caecum as a lingual thyroid at the base of the tongue in patients whose gland fails to descend. Of all ectopic thyroids, 90% are found on the lingual dorsum, where they are called lingual thyroid or ectopic lingual thyroid (1). Extra-lingual thyroid tissue is commonly located in the anterior cervical area, in the region of the thyroglossal duct. In addition ectopic thyroid tissue has been described in the submandibular region (2), trachea (3), mediastinum (4), heart (5), lung (6), duodenum (7) and adrenal gland (8). As the majority of patients with lingual thyroid are asymptomatic, the true incidence is unknown. However obstructive symptoms and hypothyroidism may be observed (9). Ugar-Cankal et al reported that the prevalence of lingual thyroid in Turkish schoolchildren in Ankara was 0,1% (10). The clinical management of lingual thyroid remains controversial. Adjustment of the treatment depends on the presence or absence of symptoms. We reported a case of primary hypothyroidism due to non-functional ectopic thyroid tissue in the lingual areas in a 16-year-old female patient. Case Report A 16 year-old girl applied for our outpatient clinic for growth retardation, primary amenorrhea,