Accuracy of Ultrasonography to Establish the Diagnosis and Aetiology of Permanent Primary Congenital Hypothyroidism

Objective: To compare ultrasonography and 99mTc thyroid scintigraphy for the aetiologic diagnosis of permanent congenital hypothyroidism (CH).

Study Design: Eighty-eight consecutive patients with CH were recruited at an endocrinology outpatient clinic and submitted to high-frequency ultrasonography and to 99mTc scintigraphy.

Results: Seventy-six patients were diagnosed with permanent CH and 12 with transitory CH. The agreement between ultrasound and scintigraphy was very high (kappa coefficient = 0.866; P < 0.001) for the entire group. In permanent CH patients, ultrasonography identified 67 cases of dysgenesis (absence of thyroid gland in the usual anatomical location in 66 and hemiagenesis in one), and this diagnosis was confirmed by scintigraphy (absence of functional thyroid tissue in 43 and ectopia in 24). In the other nine permanent CH patients, the thyroid was in the usual anatomical location on ultrasonography but scintigraphy did not identify functional tissue in one patient. In the 12 transitory CH patients, a normally shaped thyroid was detected by ultrasound in the usual location, whereas scintigraphy showed absence of functional tissue in two identical twins and scarce concentration of isotope in a third patient.

Conclusion: Ultrasonography is an accurate method to establish the presence of dysgenesis and might be used as the first imaging tool in patients with CH, whereas scintigraphy should be used mainly to distinguish agenesis from ectopia. Further examination is required to differentiate permanent CH with a normally located and shaped gland from transitory hypothyroidism.