Thyroid function profile in cord blood and postnatal changes at 24 and 72hours in healthy term Nigerian neonates

Abstract

Background: Studying the acute postnatal changes of newborn thyroid  function is essential for determining the best timing of screening for  congenital hypothyroidism. There is paucity of literature on neonatal  thyroid function and particularly the postnatal changes in Nigeria.

Objectives: To describe the profile of thyroid function in cord blood and the postnatal changes at 24hours and 72hours in healthy term neonates  delivered in Usmanu Danfodiyo University Teaching Hospital (UDUTH), Sokoto.

Subjects and methods: This was a prospective, descriptive and cross sectional study conducted over a six month period (between July-December 2009). Forty seven consecutively delivered healthy term neonates had their serum T3, T4, TSH assayed at birth, 24 and 72hours using the Enzyme linked immunosorbent assay (ELISA) technique. Data obtained are presented as mean, median and standard deviation (SD). Paired- t- test
was used for statistical inference.

Results: The mean (SD) of the serum hormone concentrations in cord blood, and venous blood at 24hours and 72hours, respectively were as follows: T3, 0.58 (0.56) nmol/l, 1.15 (0.77)nmol/l, 0.83 (0.74)nmol/l; T4, 91 (83.1)nmol/l, 121.5 (106.4)nmol/l, 104.2 (84.2) nmol/l; and TSH, 5.95 (5.81)mU/l, 8.61 (8.34)mU/l, 2.52 (2.61) mU/ l.. The mean serum T3, T4 and TSH at 24hours were higher than cord blood levels (p<0.001, 0.03, 0.05 respectively). The mean serum T3 and T4 at 72hours, were higher
than cord blood levels (p = 0.07, 0.44), whereas TSH at 72hours was significantly lower than cord blood levels; (p<0.001).

Conclusions: There was a rise, above cord level, of T3, T4 and TSH at 24hours, and a decline at 72hours, the latter being most marked in TSH. It is recommended that serum TSH taken at or greater than 72hours of life may be utilized for screening for congenital hypothyroidism in term babies,
using postnatal age appropriate reference ranges. Serum T3, T4 should then be assayed for confirmation in all neonates with a positive TSH screening.

Key words: Thyroid profile, postnatal changes, Term, Healthy neonates.