What condition is associated with macroglossia of the newborn tongue?

Macroglossia, or an enlarged tongue, in a newborn can be associated with several conditions, but hypothyroidism is particularly notable. In congenital hypothyroidism, the thyroid hormone deficiency can lead to various physical manifestations, including macroglossia. This is because thyroid hormones play a crucial role in growth and developmental processes in the body, and a deficiency during prenatal or postpartum development can lead to characteristics such as a disproportionately large tongue.

In contrast, ankyloglossia (often referred to as "tongue tie") is a condition where the tongue is tethered to the floor of the mouth by a short frenulum, leading to functional limitations of the tongue rather than an increase in size. Caput succedaneum and cephalohematoma both refer to conditions related to head trauma at birth and do not typically cause tongue enlargement. Caput succedaneum is characterized by swelling of the soft tissues of the head, while cephalohematoma involves bleeding between the skull and the periosteum. Neither of these conditions is associated with the structural enlargement of the tongue seen in macroglossia.