The purpose of this study was to establish the normal dimensions of th
e thyroid gland in euthyroid neonates. Ultrasonographic evaluation of
the thyroid gland was performed in the first week of life in 68 term n
eonates whose gestational ages at birth were 37 to 41 weeks and whose
birth weights ranged from 2570 to 4790 g. Measurements of the thyroid
lobes were done in transverse, anteroposterior, and longitudinal plane
s. All neonates had age-appropriate thyroid stimulating hormone levels
at birth. Mean +/- 2 standard deviations for thyroid volume were 472
mm(3) and 1430 mm(3). The mean measurements for the sum of both lobes
for transverse, anteroposterior, and longitudinal dimensions were 13.9
mm, 15.1 mm, and 34.6 mm, respectively. No significant correlation of
these measurements was found for gestational age, birth weight, or th
yroid-stimulating hormone levels. The correlation coefficient between
these measurements and total volume was 0.64 or less. Term euthyroid n
eonates were found to have a thyroid gland volume ranging between 472
mm(3) and 1430 mm(3). In term neonates sonographic measurements of thy
roid lobes should be obtained in all three planes for reliable assessm
ent of thyroid volume.