Sonographic measurements of the neonatal thyroid gland.

The purpose of this study was to establish the normal dimensions of the thyroid gland in euthyroid neonates. Ultrasonographic evaluation of the thyroid gland was performed in the first week of life in 68 term neonates 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 planes. All neonates had age-appropriate thyroid stimulating hormone levels at birth. Mean +/- 2 standard deviations for thyroid volume were 472 mm3 and 1430 mm3. 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 thyroid-stimulating hormone levels. The correlation coefficient between these measurements and total volume was 0.64 or less. Term euthyroid neonates were found to have a thyroid gland volume ranging between 472 mm3 and 1430 mm3. In term neonates sonographic measurements of thyroid lobes should be obtained in all three planes for reliable assessment of thyroid volume.