Elsevier

The Journal of Pediatrics

Volume 143, Issue 3, September 2003, Pages 296-301
The Journal of Pediatrics

Original articles
Follow-up of newborns with elevated screening T4 concentrations

https://doi.org/10.1067/S0022-3476(03)00184-7Get rights and content

Abstract

Objective

To determine the type and incidence of hyperthyroxinemic disorders detected by follow-up of infants with elevated screening total T4 (TT4) values.

Study design

Infants born in Oregon with a screening TT4 measurement >3 SD above the mean were offered enrollment. Serum TT4, free T4, total T3, free T3, and thyroid-stimulating hormone concentrations were measured in study infants and their mothers.

Results

Over a 20-month period, 101 infants (51 boys) and their mothers enrolled in the study (of 241 eligible infants), from a total screening population of 80,884; 17 infants were identified with persistent hyperthyroxinemia (TT4 >16 μg/dL). Ten had thyroxine-binding globulin excess (1:8088), 5 had evidence for increased T4 binding but not thyroxine-binding globulin excess (1:16,177), and 2 had findings compatible with thyroid hormone resistance (1:40,442); the other 84 infants had transient hyperthyroxinemia. Sequence analysis revealed a point mutation in the thyroid hormone receptor-β gene in one infant with thyroid hormone resistance; no mutation was identified in the other infant.

Conclusions

Although neonatal Graves' disease occurs in approximately 1 in 25,000 newborn infants, we did not detect any case among 80,884 infants, most likely because their mothers were receiving antithyroid drugs. Although the other hyperthyroxinemic disorders in the aggregate occur frequently (1:4758) and may benefit from detection, in general they do not require treatment.

Section snippets

Methods

Infants born in Oregon and undergoing newborn screening were eligible for the study. T4 screening tests are carried out by the Oregon State Public Health Laboratory (PHL) on approximately 350 Oregon infants daily. Two routine screening specimens are collected in Oregon, the first at approximately 2 days of life and the second at approximately 2 weeks of life. As the serum TT4 rises and peaks 24 hours after birth and then falls over the next week of life, samples collected at approximately the

Results

Over a 20-month period, we enrolled 101 infants (51 boys) into the study of 241 eligible infants whose mothers were offered participation, from a total screening population of 80,884 infants born in Oregon over that time. Of the 101 infants who participated, 17 had persistent TT4 elevation confirmed on serum testing, whereas the serum TT4 measurement in the other 84 infants was normal. A comparison of the screening test results in the 17 infants with persistent hyperthyroxinemia and the 84

Discussion

Overall, we detected 17 infants with confirmed hyperthyroxinemia of 80,884 newborn infants. The incidence of these combined disorders is approximately 1 in 4750, which, as described above, probably is an underestimate. Our main goal in follow-up of newborn infants with elevated screening T4 concentrations was to detect infants with some form of hyperthyroidism who would benefit from early detection and treatment. However, we did not detect any infant with unrecognized neonatal Graves' disease

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