Urinary free T4 and T3 in healthy infants and during noise exposure

Abstract

There is concern about noise exposure in the hospital environment and its effects on infants.Stress reactions are difficult to measure especially in this age group.Timed 12 h urine collections were made in 86 reconvalescent infants to determine normal day/night excretion.Collections were also made before,during and after standardized 70 or 80 dB broadband noise exposure. Ethics Committee approved,after undisturbed sleep was demonstrated in some infants,which was confirmed later throughout the study in 43 infants.

T4 and T3 were determined by RIA after extraction,incubation and elution using Sephadex columns(Habermann, 1976).Intraassay variation was 5.6 and 5.4% for T4 and T3 resp.Interassay variation along the steep part of the standard curve was 8.1-11.7% for T4 and 8.1-9.9% for T3.Recoveries were 109 ± 8 and 109 ± 7% (x̄ ± s) for T4 and T3 resp.

Median and ranges below 5 wks. were 0.185(0.068-0.527) μg/day for T4 and 0.145(0.042-0.388) for T3.For ages 5 - 45 wks.T4 was 0.227(0.047-0.501)and T3 0.326(0.073-0.605).Higher T3 values reflect iodine deficiency.There was no difference between day/night or after the noise.

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