Ectopic Thyroid Masquerading as Pituitary Adenoma

To the Editor: We reported 2 cases of ectopic thyroid gland (ETG) masquerading as pituitary adenoma (PA). The first case was a 15‐year‐old boy with growth, and mental retardation whose height was 121 cm and weight was 44 kg on admission. Bone age development index was 40, while bone age showed 6–10 years old. Magnetic resonance imaging (MRI) revealed pituitary hyperplasia [Figure 1a]. Thyroid ultrasonography did not found thyroid on the anterior aspect of the neck and the normal position of thyroid gland. The peak value of growth hormone experiments was 1.8 μg/L. Gonad function indicated testosterone (T) 0.55 nmol/L, luteotropic hormone <0.07 U/L, and follicle‐stimulating hormone 2.64 U/L. Thyroid function showed serum free T4 (FT4) 5.34 nmol/L and thyroid stimulating hormone (TSH) >150 mU/L. After treatment with eltroxin, the patient was 21 cm higher than before in one year and his intelligence improved significantly comparatively. MRI FT4 9.07 pmol/L, TSH >150 mU/L, and 15 minutes serum prolactin was 2.66 μg/L. Gonad function, 8 after midnight (AM) serum adreno‐cortico‐tropic‐hormone, and 8 AM serum cortisol were normal. Thyroid ultrasonography did not found thyroid at the normal position. History revealed that the patient was found thyroglossal cyst in 15 years old and accepted total excision of thyroglossal duct cyst in 18 years old. Then eltroxin was prescribed, and the patient was pregnant successfully in 7 months. Now, her menstruation is normal, and galactorrhea is rarely happen. These two cases were ectopic thyroid masquerading as PA. At present, classification of PA is based on plasma hormone levels or immunohistochemical staining, clinical features are always complex and confusing. In these two cases, retardation, infertility, and amenorrhea were not arising from PA, while the primary ectopic thyroid was the culprit. It caused primary hypothyroidism, TSH cell proliferation, and compensatory pituitary gland hyperplasis. Ectopic Thyroid Masquerading as Pituitary Adenoma