Normative Values for Thyroid Volume and Tracheal Index in Healthy Turkish Newborns in an Iodine Sufficient Region

INTRODUCTION: The study aims to determine the normal values of thyroid volume and tracheal index in healthy term newborns born in an iodine-sufficient population. Additionally, we investigated the usability of a handheld device for assessing the tracheal index.
METHODS: Thyroid imaging was performed at 0-2 days and 15-30 days using handheld and portable ultrasound devices. Thyroid volume and tracheal index were calculated using standard formulas.
RESULTS: A total of 144 healthy term newborns with a mean birth weight 3230 g were enrolled. The normal thyroid volume for the entire population was 0.66 ± 0.25 ml at 0-2 days, which significantly increased to 1.12 ± 0.33 ml at 15-30 days (p<0.01). There were no significant differences in thyroid volume between genders in either age group (p=0.246 and p=0.879). Thyroid volume correlated with birth weight, length, and head circumference, with the strongest correlation being with birth weight (r=0.404, p<0.001; r=0.252, p=0.002; r=0.223, p=0.007, respectively). The tracheal index at 0-2 days was 1.84±0.30 in girls, 1.82±0.27 in boys, and 1.83±0.29 overall. At 15-30 days, it was 1.99±0.23 in girls, 2.00±0.28 in boys, and 1.99±0.25 overall. Similar to thyroid volume, the tracheal index increased with age (p<0.01), with no significant gender differences in either age group (p=0.593 and p=0.886). Thyroid volume and tracheal index were moderately correlated in both measurements (rho=0.538, p<0.01). Measurements of the trachea, and thyroid lobe widths using portable and handheld ultrasound devices were correlated (r=0.449, p<0.01; r=0.638, p<0.01; r=0.497, p<0.01). There was also a correlation between tracheal index measurements using both devices in both the first and second measurements.
DISCUSSION AND CONCLUSION: This study provides normative data on thyroid volumes and tracheal index in newborns from an iodine-sufficient population. The tracheal index can estimate thyroid size when volume calculation is not feasible and handheld ultrasound devices are effective for this assessment.