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

Objective: This study aimed to determine the normal values of thyroid volume and tracheal index in healthy, term newborns born in an iodine-sufficient population. Moreover, the usability of a handheld device for assessing tracheal index was assessed.

Methods: Thyroid imaging was performed at 0-2 days and 15-30 days using handheld and portable ultrasound (US) devices. Thyroid volume and tracheal index were calculated using standard formulae.

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 significantly 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 US devices were positively 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 at both the first and second measurements.

Conclusion: This study provides normative data for thyroid volumes and tracheal index in newborns from an iodine-sufficient population. The tracheal index may be used to estimate thyroid size when volume calculation is not feasible. Handheld US devices are effective for this assessment.