The role of serum thyroglobulin concentration and thyroid ultrasound imaging in the detection of iodide transport defects in infants

Abstract

When discovered by neonatal screening, a thyroid dyshormonogenesis is usually not recognized as a goitre. Especially a total iodide transport defect can easily be misclassified as thyroid agenesis, since radionuclide imaging cannot visualize the thyroid. We present the only iodide transport defect ever discovered in the Netherlands, the 35th reported in the literature, and the first one found exclusively as a result of neonatal screening. We demonstrate that iodide transport defects, in common with organification and deiodinase defects, can be distinguished from thyroid dysgenesis by demonstrating a normal or enlarged thyroid ultrasound image, and especially by measuring very high serum thyroglobulin levels (above 1000 pmol/l). In the presented case, an iodide-123 saliva-to-serum ratio near unity completed the etiologic classification. Measurement of serum thyroglobulin levels, in combination with thyroid ultrasound imaging, will improve the early identification of hereditary types of congenital hypothyroidism, and especially iodide transport defects, in patients found by neonatal thyroid screening.

Sodium/Iodide Symporter Mutant V270E Causes Stunted Growth but No Cognitive Deficiency

“…In this context, the increase in TSH levels following a reduction in thyroid hormone production might have partially overcome the defect in trafficking of V270E NIS to the plasma membrane by enhancing NIS transcription, as occurred in ITD patients carrying the missense mutation T354P (35). Consistent with this possibility, the proband's high serum thyroglobulin levels indicate TSHinduced overstimulation of the thyroid tissue (36).…”

Molecular Biology and Functions of Carrier Proteins. Annual Symposium (46th) of the Society of General Physiologists held in Woods Hole, Massachusetts on September 10-13, 1992. Volume 48

“…The I-transport system of the thyroid itself is rarely the primary target of thyroid disease. However, several cases of hypothyroidism caused by a specific partial or total congenital defect of the V transport system, a condition of considerable research interest, have been reported over the years (Leger et al, 1987;Vulsma et al. 1991).…”