Normal Thyroid Gland Size in Newborns
The normal thyroid gland volume in a term newborn ranges from approximately 0.5 to 1.4 mL (472-1430 mm³), with a median volume around 1.0 mL, as measured by ultrasound in the first week of life. 1, 2
Specific Dimensional Measurements
For term newborns examined in the first week of life, the thyroid gland dimensions are:
Right lobe measurements:
- Width: 0.7 cm (range 0.5-1.0 cm) 1
- Depth: 0.7 cm (range 0.5-1.0 cm) 1
- Length: 2.1 cm (range 1.5-2.9 cm) 1
- Volume: 0.5 mL (range 0.2-0.9 mL) 1
Left lobe measurements:
- Width: 0.7 cm (range 0.5-1.0 cm) 1
- Depth: 0.7 cm (range 0.5-1.0 cm) 1
- Length: 2.0 cm (range 1.6-2.7 cm) 1
- Volume: 0.5 mL (range 0.3-1.0 mL) 1
Combined thyroid volume: 1.0 mL (range 0.5-1.8 mL) 1
Clinical Context and Assessment
Ultrasound is the preferred method for accurate thyroid gland assessment in newborns, as it provides precise volumetric measurements and is superior to clinical palpation alone. 1, 2 Measurements should be obtained in all three planes (transverse, anteroposterior, and longitudinal) for reliable volume assessment. 2
Important Considerations:
No correlation with gestational age or birth weight: In term euthyroid neonates (37-41 weeks gestation), thyroid volume does not significantly correlate with gestational age, birth weight, or TSH levels. 2
Population variations exist: Reference ranges may differ between populations, emphasizing the importance of using region-appropriate normative data when available. 1, 3
Timing of assessment: These measurements are typically obtained within the first week of life in healthy term newborns. 1, 2
Clinical Pitfalls to Avoid
Do not rely on visual or palpation assessment alone to determine if a thyroid gland is abnormally sized—quantitative ultrasound determination is more accurate than clinical criteria for diagnosing goiter or hypoplasia. 4
Be aware that newborn screening for congenital hypothyroidism is offered throughout the United States and should be performed in all infants, as early treatment in the first several weeks of life can result in nearly normal intelligence and growth. 5, 6