Congenital hypothyroidism in newborns tied to excess maternal iodine supplements

Congenital hypothyroidismCongenital hypothyroidism in newborns is tied to excess maternal iodine supplements. Congenital hypothyroidism is a thyroid deficiency at birth. If not treated, it can contribute to neurocognitive impairments. The U.S Institute of Medicine recommends an upper limit of 1,100 µg of iodine during pregnancy to be safe for the fetus.

Research conducted by Dr. Kara Connelly found three cases of congenital hypothyroidism where the mothers took triple the amount of recommended iodine while pregnant or breastfeeding. This suggests too much iodine may contribute to the thyroid hormone deficiency. Iodine is transferred to the infant through the placenta and breastfeeding. The children in the study had 10 times greater levels of iodine, compared to healthy newborns.


Too much iodine temporarily decreases thyroid function in order to protect against an overactive thyroid (hyperthyroidism). Immature thyroids in fetuses and newborns do not possess this protective effect, which puts them at a greater risk for excess iodine-induced hypothyroidism.

Dr. Connelly said, “The use of iodine-containing supplements in pregnancy and while breastfeeding is recommended in the United States. However, these cases demonstrate the potential hazard of exceeding the safe upper limit for daily ingestion.”

Pregnant women and mothers should discuss the use of nutritional supplements with their doctors to determine proper dosage.

Congenital hypothyroidism causes and symptoms

There are numerous reasons as to why a newborn develops congenital hypothyroidism, including a missing or poorly developed thyroid gland, a pituitary gland that does not stimulate the thyroid, poorly formed thyroid hormones or thyroid hormones that do not work, medications the mother has taken during pregnancy, lack iodine or excess iodine during pregnancy, and antibodies created by the mother’s body blocking thyroid function of the fetus.

Symptoms of congenital hypothyroidism include a dull look, puffy face, thick tongue that sticks out, choking episodes, constipation, dry brittle hair, jaundice, lack of muscle tone, low hairline, poor feeding, short height, sleepiness, and sluggishness.

Congenital hypothyroidism prevention and treatment

Prevention of congenital hypothyroidism involves proper iodine levels (not too little or too much), watching what kind of medications the mother takes during pregnancy, and not avoiding iodine-supplementing salts. Many states also conduct hypothyroidism screenings in newborns. If your particular state does not, speak with your doctor about potentially having your child screened.

Treatment for congenital hypothyroidism should begin immediately after diagnosis. The most common treatment is thyroxine, which is followed up by routine blood tests to monitor thyroid hormone levels in the blood.

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