May hypothyroidism lower intelligence IQ

Congenital hypothyroidism

One in about 3000 to 4000 newborns is born with congenital hypothyroidism, that is, an underactive thyroid [1]. The consequences for the young patients can be severe physical and mental disabilities. However, early therapy prevents this and enables those affected to lead a normal life.

A functioning thyroid is crucial for physical and mental development in childhood. In contrast to adults, untreated functional disorders quickly lead to severe permanent damage. The thyroid gland and its control system consisting of the pituitary gland and hypothalamus develop in the first twelve weeks of pregnancy. After that, the fetus begins to produce thyroid hormones on its own.

Hypothyroidism in newborns

Congenital hypothyroidism, also known as congenital or connatal, occurs in around 1 in 3,000 to 4,000 newborns. This makes it one of the most common congenital diseases of the endocrine system in industrialized nations. In certain developing countries with iodine deficiency, every 50th newborn is affected [1].

The development of the disease can be traced back to two causes. On the one hand, there are genetic disorders in the production of thyroid hormones. This affects around 10 to 20 percent of children. The thyroid gland is normal or significantly enlarged. On the other hand, morphological abnormalities are responsible for the hypothyroidism. These include malformations of the thyroid gland, thyroid tissue in other places (for example at the base of the tongue) or a completely missing thyroid gland (athyroidism). This is the case in the majority of patients [2]. There is also the variant of transient, i.e. temporary, congenital hypothyroidism. This is caused either by maternal antibodies or by severe iodine contamination during pregnancy, which inhibit the child's thyroid.

In all cases, the symptoms are very minor immediately after the birth, as the need for thyroid hormone could still be covered by the mother until then. After a few weeks, however, the infants notice slow motor and physical development or they become tired more quickly when breastfeeding. If the disease remains untreated, severe physical and mental disabilities and hearing impairments can occur in many cases [2].

The earlier the treatment, the better

In Germany, newborn screening also routinely examines thyroid function. If the TSH (thyroid stimulating hormone) values ​​are abnormal, the thyroid hormones T3 and T4 are checked, which are then used to make the diagnosis. Early treatment with levothyroxine, if possible within the first 14 days of life, prevents or reverses the symptoms [2]. The affected children can then lead a normal life with appropriate therapy.

The therapy control consists of a physical examination as well as the determination of TSH, T4 and, if necessary, T3. This should be repeated at short intervals of a few weeks at the start of treatment. Subsequent checks every three months for the first two years of life are sufficient. Mental (cognitive) development is age-appropriately checked once in the first two years and before starting school [2].

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[1] Grüters-Kieslich A. (2014) Diseases of the Thyroid. In: Hoffmann G., Lentze M., Spranger J., Zepp F. (eds) Pediatrics. Springer, Berlin, Heidelberg
[2] Guideline: Diagnosis, Therapy and Follow-Up of Primary Congenital Hypothyroidism Responsible for guidelines Prof. H. Krude, Berlin (status: November 2010)