Serum thyroglobulin levels in preterm infants with and without respiratory distress syndrome. II. A longitudinal study during the first 3 weeks of life

Serum thyroglobulin (Tg) and thyroid-stimulating hormone (TSH) levels were measured in 182 preterm and term infants. Samples were taken from cord blood, and at 1, 3, 7, 14, and 21 days after birth. The infants were divided into groups according to their perinatal characteristics: infants who were appropriate for gestational age, infants who were small for gestational age, and preterm infants who developed respiratory distress syndrome. These groups were subdivided according to gestation age. Tg serum levels showed a significant increase in the 1st day in all groups, and decreased significantly after about 1 wk. The highest Tg levels were found in the 1st wk of life in respiratory distress syndrome infants, and in infants with the lowest gestation ages. TSH levels increased at day 1 but only in appropriate and small for gestational age infants of more than 30 wk of gestation. TSH levels at day 1 in the groups with gestation ages of less than 30 wk and in respiratory distress syndrome infants of more than 30 wk were low, reflecting a low TSH surge. We conclude that the neonatal increase of Tg is not merely caused by the TSH surge. We suggest that the Tg increase is due to an impaired degradation of Tg, and/or to hemoconcentration, which are more pronounced in respiratory distress syndrome infants compared with appropriate for gestational age infant

Concentration of plasma thyroglobulin and urinary excretion of iodinated material in the diagnosis of thyroid disorders in congenital hypothyroidism

In this paper we describe methods for the early aetiological diagnosis of congenital hypothyroidism, using beside the classical T4, T3 and TSH plasma concentrations, four additional parameters in plasma and urine. The first one is thyroglobulin (Tg). In normal children of more than one year of age and in adults, 5-35 ng/ml plasma is found, in neonates 2-3 weeks old, this level is 10-250 ng/ml. In patients with a stimulated thyroid gland, as in primary congenital hypothyroidism, plasma Tg levels increase. High Tg values are found in iodine deficiency and in organification defects. In the absence of the thyroid gland plasma Tg is undetectable. Low to normal levels are found in cases with hypoplasia of the gland. In patients with a disturbed synthesis of Tg, resulting in Tg deficiency of the gland, plasma Tg levels vary from undetectable to normal. The PBI-T4 plasma difference, which is caused by circulating abnormal iodoproteins is the second parameter. The products of thyroidal breakdown processes of the abnormal iodoproteins are excreted in the urine and used as the third parameter. We found that the excretion of this low molecular weight iodinated material (LOMWIOM) was increased only in Tg-deficient patients. If the neonate is found to be hypothyroid, thyroid hormone substitution must be given immediately. Blood and urine sampling can be done just before or even directly after starting the therapy. The measurements extended with the determination of the total iodine excretion (fourth parameter) can be carried out within 1 week. With these additional methods it appeared to be possible to distinguish between several types of congenital hypothyroidism in neonates found by screenin

Serum thyroglobulin levels: the physiological decrease in infancy and the absence in athyroidism

The cord serum thyroglobulin levels of 218 neonates are much higher than the levels after the first year of life and show a wide range. A relation exists between a shorter gestational age and increased thyroglobulin levels. The serum thyroglobulin levels decrease within a few months after birth, but throughout the first year of life, these levels are still higher than the normal values at later ages (5-35 ng/ml). IN 3 athyroid children, thyroglobulin is undetectable in seru

The human thyroglobulin gene contains two 15-17 kb introns near its 3'-end.

We have cloned overlapping segments of the human thyroglobulin gene from a genomic cosmid library. Restriction mapping and electron microscopy show that a region of 38 kb at or near the 3'-end of this gene encodes only 850 nucleotides or 10% of the messenger RNA (mRNA) sequence. The region contains five exons of 130-210 nucleotides, split by introns of 1 to 15-17 kb. This represents the lowest ratio of coding to non-coding DNA (2.2%) found thus far in any eukaryotic gene. Blot hybridization under non-stringent conditions shows the presence of only one copy of this gene in the human genome and the absence of other closely related sequences