Introduction: Primary congenital hypothyroidism (PCH), defined as thyroid hormone deficiency, can be viewed as an anatomical, clinical, biochemical and radiological spectrum.
Its etiology includes thyroid dysgenesis (85%) with defects in thyroid gland development and thyroid dyshormonogenesis (15%) with inborn error of thyroxine synthesis or release.
There is growing evidence that precise characterization of thyroid dysfunction by dual imaging, scintigraphy and ultrasound (US) is helpful in improving both medical care and understanding of the underlying disease.
Scintigraphy is the gold standard method for assessing the diagnosis of ectopic thyroid tissue and color Doppler US can accurately measure the thyroid volume, reveal additional information regarding the anatomy of the gland and possible remnant of the thyroglossal duct.
We report 2 consecutive cases of PCH in which the dual imaging use allowed precise etiology.
Case presentation: Case 1. An 8-day-old female presented with prolonged jaundice and lethargy. Neonatal screening revealed a thyroid-stimulating hormone (TSH) level >100 µIU/mL. Repeat serum thyroid function tests, TSH >200 µIU/mL (0.20 4.20), thyroxine (T4) 1.8 pg/mL (7 - 17), triiodothyronine (T3) 0.4 pg/mL (0.9-1.95), thyroglobulin 500 µg/L (1.4 - 78), confirmed the primary hypothyroidism with both epiphysis absent on X-ray of the knee.
US scan of the neck was suspicious of thyroid agenesis and described a thyroglossal duct cyst. The nuclear scan (123I) found an ectopic thyroid tissue in the wall of thyroglossal duct cyst. The wall of a thyroglossal duct cyst is the second most common site for ectopic thyroid.
Case 2. An 8-day-old male newborn presented with hypo activity. Neonatal screening was highly suggestive of congenital hypothyroidism. The report of TSH 50 mIU/mL, T4 4 pg/mL,
T3 1 pg/mL, and thyroglobulin 249 µg/L confirmed the diagnosis. X-ray of the knee showed normal ossification centers.
Neck ultrasound suggested hypoplasia of the thyroid tissue and described a thyroglossal duct cyst.123I scintigraphy yielded the final diagnosis of hemiagenesis, with absent left lobe.
Conclusion: Dual imaging allowed a specific diagnosis of the disorders of development of thyroid and abnormal obliteration of the thyroglossal duct. US and scintigraphy, as part of the optimal management of PCH, are complementary and provides the clinician maximal information on the anatomic and functional status of the thyroid. Parents can be counseled on either the certainty of lifetime treatment (dysplastic thyroid) or the possibility of later discontinuing therapy (eutopic thyroid). Neonatal thyroid imaging requires an extensive amount of experience.
19 Sep 2019 - 21 Sep 2019