Hypothyroidism congenitalE03.1

Congenital hypothyroidism is a pathological metabolic condition that already exists at birth with insufficient supply of thyroid hormones to the organism. It is the most common congenital disease of the endocrine system and occurs in the most vulnerable phase of brain development. If left untreated, it leads in many cases to severe physical and mental disability. These effects can be improved or prevented by treatment with L-thyroxine in the first weeks of life. Congenital hypothyroidism is the most common preventable cause of mental retardation.

Permanent primary congenital hypothyroidism: is caused in about 85% of cases by a developmental disorder of the thyroid gland (dysgenesis).

• Ectopy (about 70%) with scintigraphically detectable thyroid tissue between the base of the tongue and the pre-tracheal position as a result of a disturbed embryonic migration process.
• Hypoplasia/hemiagenesia (5%) in pre-tracheal position: rare; progresses insidiously in the first weeks of life and is therefore often misjudged.

• Athyreosis: about 25% of cases; represents the most severe form with complete absence of thyroid tissue.

Incidence: 1: 3270 births; congenital hypothyroidism is the most common congenital endocrinopathy

The normal development of the brain in utero and postnatally is highly dependent on an adequate supply of thyroid hormones. This is why the expression of thyroid hormone receptors in the embryonic brain already occurs in the first trimester.

The classic clinical signs of congenital hypothyroidism are present in only about 5% of patients at birth. They develop during early childhood. The children are described as calm, with long sleep phases and lazy drinking. Nevertheless they gain weight rapidly.

Typical signs of congenital hypothyroidism are:

• prolonged jaundice
• large fontanel (especially posterior)
• hypotension, adynamia, short waking phases
• Drinking weakness
• Rapid weight gain despite laziness
• Hypothermia
• Macroglossia
• Increasingly rough facial features
• Umbilical hernia

The treatment must be carried out immediately after acceptance of the confirmatory diagnosis. Any time delay should be avoided in this extremely vulnerable phase of brain development. Levothyroxine p. o. in a dose of 10-15µg/kgKG/d is the therapy of choice. Early and high-dose therapy can also minimize the risk of IQ loss in severe hypothyroidism by normalizing the peripheral thyroid hormones in the blood as quickly as possible. The tablets should be crushed and administered with 1-2 ml water or breast milk.

Neonatal screening