Which physical sign is associated with congenital hypothyroidism?

Large anterior and posterior fontanels can indicate congenital hypothyroidism due to developmental delays associated with inadequate thyroid hormone levels. In newborns, the presence of a large fontanel may be attributed to insufficient bone mineralization and overall growth, which are directly influenced by thyroid hormones. These hormones are crucial for growth and brain development in neonates. Without adequate levels, infant growth patterns can be adversely affected, leading to conditions such as open or larger fontanels.

In contrast, increased muscle tone is generally not associated with congenital hypothyroidism; instead, a hypotonic state is more common. Pale skin may be observed in various conditions but is not a definitive sign of congenital hypothyroidism. Rapid weight gain is often a sign of other conditions such as metabolic syndromes rather than a hallmark of hypothyroidism, where infants typically exhibit poor weight gain due to inadequate metabolic function. Thus, assessing the size of the fontanels is vital in understanding potential thyroid abnormalities in infants.