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

There is concern about noise exposure in the hospital environment and its effects on infants. Stress reactions, however, are difficult to measure, especially in this age group. Urinary T4 and T3 have proved to be equivalent to catecholamine determinations in helicopter pilots and in motion sickness. They represent the free fraction of thyroid hormones in serum. Timed collections of urine were made in 78 healthy infants and in 43 infants exposed to standardized noise. T4 and T3 were determined by RIA on Sephadex columns. Medians and ranges are given for day and night and before, during and after noise exposure.