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 after treatment showed pituitary hyperplasia significantly regressed [Figure 1b]. The second case was a 27-year-old female with galactorrhea, amenorrhea, and infertility. MRI showed the signal was obviously abnormal (uniform strengthening) in the saddle pituitary, the size was 1.0 cm × 1.5 cm × 1.6 cm, which indicated the PA was huge [Figure 1c]. Thyroid function showed 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.

Figure 1

(a) Magnetic resonance imaging of the 15-year-old teenager with ectopic thyroid before the treatment showed pituitary hyperplasia (black arrow), sagittal T1-weighed contrast enhanced image; (b) magnetic resonance imaging of the 15-year-old teenager with ectopic thyroid after the treatment showed significantly reduced pituitary (black arrow), Sagittal T1-weighed image; (c) magnetic resonance imaging of the 27-year-old female with ectopic thyroid before the treatment showed pituitary hyperplasia (black arrow), Sagittal T1-weighed contrast enhanced image.

ETG, the most frequent form of thyroid dysgenesis, refers to the presence of thyroid tissue in locations other than the normal anterior neck region.[1] It remains a rare disease.[12] Moreover, females account for 65–80% of ETG cases.[3] Although ETG has been understood gradually, diagnostic delay in ETG remains common, and this delay compounded with inappropriate therapeutic methods is responsible for the poor outcome in affected patients, especially in adolescents and women with childbearing age. When aberrant thyroid was totally excised, thyroid function would be absent or inadequate permanently. Substitute therapy would be essential, cost unpleasantly high and therapeutic period, unfortunately, life-long time. Thereby, thyroid function test and color Doppler ultrasonography are necessary when PA is considered. If ETG is suspected, preoperative analysis is of particular significance. A high index of clinical awareness and education of clinical practitioners will help a great deal in improving the ultimate outcome in patients with ETG.

Financial support and sponsorship

The work was supported by grants from the Chinese National Natural Science Fund (No. 30900543), the Clinical Science Fund of PLA General Hospital (No. 2013FC-TSYS-1028) and the Beijing Natural Science Fund (No. 7152136).

Conflicts of interest

There are no conflicts of interest.