295 SERUM THYROID STIMULATING HORMONE (TSH), THYROXINE (T₄) AND TRIIODOTHYRONINE (T₃) LEVELS IN THE PRE-TERM INFANT

Abstract

To determine if inclusion of the healthy pre-term infant in mass neonatal screening programs would increase the number of false-positive results, the changes in serum TSH, T₄ and T₃ levels were studied in healthy infants between 30 and 35, Group (G) I, and 36 to 38, G II, weeks gestation during the 1st 72 hours (h) of age.

In both G there was a rise in the mean serum TSH level at .5 to 4 h after birth. Mean T₄ and T₃ levels increased by 24 h and remained unchanged until 72 h of age, although the rise in mean T₃ level was less in the younger gestational age infant. Conclusions: 1) In the healthy pre-term neonate, the rise in serum TSH level at .5 to 4 h of age is followed by a rise in serum T₄ and T₃ levels by 24 h. 2) Screening of healthy pre-term infants from 30 to 38 weeks gestation for congenital hypothyroidism by serum T₄ or TSH levels at 24 to 72 h will most likely not increase the number of false-positive results.

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