Long-term evolution of glycerol intolerance syndrome

Abstract

The two diagnostic tools used, ultrasonography and serum thyroglobulin determinations, were found to give complementary information about the presence and the functional state of the thyroid gland. In our athyroid patients, the absence of thyroid tissue on ultrasound evaluation was confirmed by undetectable serum Tg levels; conversely, Tg was measurable in serum when thyroid glands were visualized by sonography. In the five infants with hypoplastic thyroids glands, serum Tg levels varied widely, showing the existence of functioning thyroid tissue, although not to such a degree as to give normal serum hormone values. In these patients during thyroxine therapy, there was normalization of T4 and TSH values, with a reduction in Tg levels. A physiologic decrease of serum Tg levels has been reported during the first year of life? Our data are in accordance with the results of two recent reports ~,2 comparing serum Tg levels with thyroid scintigraphic findings in hypothyroid infants; we were able to document a similar good correlation between serum Tg levels and thyroid ultrasound data. This observation may have practical diagnostic relevance: if our results are confirmed in a larger series, the combined serum Tg assay and thyroid ultrasound evaluation may gain wide acceptance for the differential diagnosis of congenitally hypothyroid infants detected through neonatal screening programs. Thyroid ultrasound is a simple, sensitive, and noninvasive diagnostic tool that would be ideal for evaluating thyroid anatomy in early life and before therapy, possibly substituting for radionuclide scans. The functional information provided by serum Tg levels should be complemented by morphologic data obtained with ultrasound or radionuclide scan. In hypothyroid infants with undetectable serum Tg levels but with normally placed thyroid tissue, l the discordance between Tg assay and morphologic thyroid examination suggest a biosynthetic defect of thyroid hormone production ~ or a lack of thyroid stimulation caused by hypothalamic or pituitary defects.