Ultrasound Measurement of Thyroid Volume in Term Newborns

The thyroid is a fundamental endocrine gland that regulates metabolism throughout the life cycle. Thyroid's function is particularly crucial in fetuses, newborns, and children, as thyroid hormones play a key role in the development of the central nervous system. A deficiency of thyroid hormones in childbearing age women due to untreated hypothyroidism, autoimmune disorders or iodine deficiency poses a threat to both fertility and pregnancy progression and can negatively impact fetal and neonatal neurological outcomes later in life. Since the introduction of neonatal TSH- screening method the prognosis of newborn with congenital hypothyroidism has significantly improved due to early start of levothyroxine treatment. The findings of reduced or increased thyroid size in newborn with TSH elevation can support the need for further investigation such as genetic analysis. For this reason, having normative data of thyroid volume is fundamental in newborn population. According to the current guidelines for congenital hypothyroidism, the primary imaging techniques for evaluating neonatal thyroid include ultrasound and radionuclide scintigraphy. Ultrasound is the preferred modality due to its non-invasive nature and ability to provide detailed information about the gland's structure, size, position, vascularization, and echogenicity. Thyroid volume is tightly regulated during fetal development, and variations in size may indicate pathological maternal and neonatal dysfunctions. Therefore, thyroid volume measurement is a crucial indicator for monitoring the gland's development and function in newborns and is strongly associated to environmental factor such as iodine status and maternal factors. International studies conducted in countries with different iodine status and national salt iodization programs (Poland, Germany, Belgium, Turkey, United Kidgdom, United States China, Brazil) have shown significant variations in average thyroid volume values in euthyroid term newborn ranging from 0.47 in the Unites States to and 1.62 ml in the United Kingdom. These findings highlight the importance of geography and iodine supplementation in determining neonatal thyroid volume. Ultrasound of the thyroid gland was generally recorded during the first three weeks of life. However, no reference data are currently available for Italian newborns. Italy is considered an iodine sufficient area but there is an increased risk of deficiency during pregnancy. Establishing specific reference values of newborn thyroid volume for the Italian population is therefore necessary. In addition to the geographical region of origin, several maternal factors may influence neonatal thyroid volume, including levothyroxine intake in cases of hypothyroidism, nutritional iodine supply/intake, use of medications/disinfectants containing iodine, gestational diabetes and smoking during pregnancy. One study found a negative correlation between high maternal levothyroxine doses and neonatal thyroid volume. Although this correlation is weak, multivariate logistic models confirmed the impact of maternal therapy on neonatal thyroid volume. Excess maternal thyroid hormones can suppress fetal TSH secretion, limiting follicular cell proliferation, leading to a reduced neonatal thyroid volume. Studies about the association between gestational diabetes and thyroid neonatal volume reported difference results. Smoking during pregnancy has also been associated with variations in neonatal thyroid volume. Studies on adults have shown a 25% increase in thyroid volume in smokers compared to non-smokers. The high prevalence of smoking among young women in certain regions could explain an increased neonatal thyroid volume. This study is essential for establishing national reference values for thyroid volume in healthy term and preterm Italian newborns, addressing a gap in the available data. Understanding geographical differences, maternal influences, and the newborn characteristics of preterm newborns will improve the monitoring and management of neonatal thyroid conditions, with potential implications for public and neonatal health.

Healthy, born between 37 to 42 weeks of gestational age

Diagnostic Test: Thyroid ultrasound

Thyroid Ultrasound is a safe method because it does not involve ionizing radiation, is non-invasive and painless, takes only a few minutes, and does not cause discomfort. The Ultrasound machine is the Philips EPIQ 5 system (Philips Healthcare, Eindhoven, the Netherlands) with CE certification. The examination is conducted with high-frequency probes (linear hockey stick L12-20 MHz). All thyroid gland scans and measurements are performed by two trained observers at the bedside using a portable scanner. A generous amount of coupling gel is applied to the transducer surface, which is placed midline on the neck of the infant. The examination of each lobe is performed in both longitudinal and transverse projections. During the examination, the neonate is in the supine position with slight extension of the neck, while sucking on an assistant's gloved finger with glucose drops.

Plazo: First week of life

Establish reference values for normality for thyroid volume in term newborns. Measurement of the anteroposterior, mediolateral, and craniocaudal diameters (cm) of both thyroid lobes. Calculation of thyroid volume (ml) using the ellipsoid formula.

Plazo: First week of life

Correlation between neonatal thyroid volume (measured in mL by ultrasound) and neonatal weight (g), length (cm), and gestational age (weeks), expressed as Pearson or Spearman correlation coefficients as appropriate.

Plazo: First week of life

To use the data collected from healthy subjects as a reference for comparison with data from newborns affected by thyroid disorders. To analyze statistically significant volumetric differences in thyroid volume between healthy and affected infants, with the aim of developing earlier diagnostic tools or gaining a better understanding of the mechanisms underlying neonatal thyroid disorders.

Plazo: first week of life

Correlation between neonatal thyroid volume (mL, assessed by ultrasound) and serum TSH (mU/L) and FT4 (pmol/L), measured using standard laboratory assays, expressed as Pearson or Spearman correlation coefficients.

Plazo: first week of life

Correlation between neonatal thyroid volume (mL, assessed by ultrasound) and maternal urinary iodine concentration (µg/L), measured using standard urinary iodine assays, expressed as Pearson or Spearman correlation coefficients.

Plazo: first week of life

Comparison of neonatal thyroid volume (mL, assessed by ultrasound) across different ethnic groups, expressed as mean differences or regression coefficients.

Plazo: first week of life

Comparison of neonatal thyroid volume (mL, assessed by ultrasound) between groups defined by the presence or absence of maternal pregnancy-related disorders (e.g., thyroid disease, gestational diabetes, hypertension), expressed as mean differences or regression coefficients.

Ultrasound Measurement of Thyroid Volume in Term Newborns : a Single-centre Cross Sectional Observational Study