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Thyroid hormone in the blood of newborns (test for congenital hypothyroidism)
Last reviewed: 05.07.2025
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Congenital hypothyroidism may be caused by aplasia or hypoplasia of the thyroid gland in newborns, deficiency of enzymes involved in the biosynthesis of thyroid hormones, and deficiency or excess of iodine during intrauterine development. The cause may also be the action of iodine radionuclides, since from 10-12 weeks of intrauterine development the thyroid gland of the fetus begins to accumulate iodine. Clinical manifestations of congenital hypothyroidism include large body weight of the newborn; swelling of the hands, feet, face, dense skin; hypothermia; weak sucking reflex; intense weight gain.
Reference values (norm) of thyroid-stimulating hormone concentration in the blood of newborns
Age |
Neonatal TSH level, mIU/L |
Newborn |
<20 |
Day 1 |
11.6-35.9 |
Day 2 |
8.3-19.8 |
Day 3 |
1.0-10.9 |
4-6th day |
1.2-5.8 |
If congenital hypothyroidism is suspected, thyroid-stimulating hormone is determined on the 4th-5th day after birth. An increase in the level of thyroid-stimulating hormone is considered an indication for treatment with thyroid hormones. Treatment begins no later than the 5th-17th day after birth. The adequacy of the drug dose is controlled by the concentration of CT 4 and thyroid-stimulating hormone.
If hypothyroidism is combined with chronic adrenal cortex insufficiency, correction of the condition with corticosteroids and careful selection of thyroid hormone doses are necessary to avoid adrenal crisis.