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Congenital Hypothyroidism

Congenital hypothyroidism is a partial or complete loss of function of the thyroid gland (hypothyroidism) that affects infants from birth (congenital). Congenital hypothyroidism may lead to irreversible mental retardation when left untreated during the first year of a child’s life. It can be prevented with early diagnosis through the Expanded Newborn Screening and timely treatment with medications. The thyroid gland is located at the neck and is responsible for producing thyroid hormone - which has a role in metabolism and normal brain development in early life. It starts to develop during the first 3 weeks of pregnancy and continues to develop until birth. Babies with genetic anomalies may have an underdeveloped thyroid but their brain development can still be protected by the mother’s thyroid hormone while in the womb. Mothers who are iodine deficient may develop hypothyroidism and may not have enough thyroid hormone to share with the developing fetus - making the baby at high risk of also developing congenital hypothyroidism which may lead to mental retardation.

The second possible cause of this condition is excessive iodine intake or exposure during pregnancy which can turn off the thyroid glands from producing thyroid hormone due to the phenomenon called “Wolff-Chaikoff Effect”. Normally, the thyroid gland returns to normal function after the excess iodine exposure has been removed. However, preterm infants who are born before 30 weeks of pregnancy haven’t developed this function yet - making them more prone to developing hypothyroidism. Thus, it is important to prevent excessive iodine intake from food or herbal supplements, and exposure to iodine-containing antiseptics and radiographic contrast agents.

The third possible cause are medications that the mother takes during pregnancy for hyperthyroidism such as Antithyroid medications like methimazole or propylthiouracil which can cross the placenta and affect the developing fetus. Lastly, if the mother has an autoimmune thyroid disease (Grave’s Disease), the autoimmune antibodies may also cross the placenta and attack the baby’s developing thyroid and cause temporary hypothyroidism which may take 3 - 6 months to resolve. This time period may be detrimental to the baby’s brain development - thus timely detection and treatment is important.

Symptoms

• Usually asymptomatic at birth and birth weight and length may be normal unless premature. Newborn screening is needed for early diagnosis
• Earliest sign: Prolonged yellowing of the skin and eyes
• Large abdomen
• Cold and mottled skin or dry and scaly skin
• Feeding difficulties, sluggishness, lack of interest, always sleeping
• Respiratory difficulties due to large tongue
• Constipation that does not resolve with treatment
• Progressive retardation of physical and mental development (or not achieving developmental milestones)

Prevention

1. Consult your doctor if you are taking antithyroid medications before getting pregnant or while pregnantAntithyroid medications such as methimazole may hinder the baby’s developing thyroid. Consult your doctor if you are undergoing treatment for Hyperthyroidism so you can be guided in terms of medication adjustment and timing of getting pregnant.

2. Use iodized salt and eat at least 2 fish or seafood every week as a source of iodineUsing iodized salt in usual home dishes is a good source of iodine during pregnancy especially in areas with little access to fish or seafood. Other good sources include fish and seafood, seaweeds, shrimp and canned tuna.

3. Reduce goitrogen intake or food items that interfere with iodine use or thyroid hormone productionGoitrogens are substances that hinder iodine use for thyroid hormone production. They can be found in cruciferous vegetables such as cabbage, broccoli, cauliflower, soybean isoflavones especially when eaten raw or in high amounts. Their goitrogen content can be reduced by cooking.

4. Avoid exposure to high iodine containing products. Excess iodine can be found in some supplements or herbal products, iodine-containing antiseptics and radiographic contrast agents.

5. Do the Expanded Newborn Screening soon after birth. The expanded newborn screening can detect congenital hypothyroidism even if the newborn appears normal at birth. Through early diagnosis, treatment can be given as early as possible.

Treatment

The treatment for Congenital Hypothyroidism is Oral Levothyroxine - a synthetic form of thyroid hormone which is given to the infant to help support brain development during their first weeks of life. Early treatment prevents severe mental retardation and physical delays. However, some children may have mild delays in terms of reading comprehension and math skills. With continuous treatment, IQ improves by the time they reach adolescence [4].

In general, good nutrition together with appropriate medical advice during the first 1000 days of life can help prevent congenital disorders. The Expanded Newborn Screening is also a way of detecting conditions such as congenital hypothyroidism at birth. Thus, with early diagnosis and treatment complications such as mental retardation can be prevented - giving your child a chance to reach their full potential!

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References:

• Wassner, A. J. (2018). Congenital hypothyroidism. Clinics in perinatology, 45(1), 1-18.
• Punongbayan, R.A.L., Morelos, A.M.R., Tan-Lim, C.S.C., De Vera, A.S.M., Aherrera, J.A.M., Tiongson, M.D.A., Banzuela, E.P.C. (2020). Pedia Platinum, 1st ed. Quezon City: Top Practice Medical Publishing Corporation.
• Raymond, J. L., & Morrow, K. (2020). Krause and Mahan’s Food and the Nutrition Care Process E-Book. Elsevier Health Sciences.
• Newborn Screening Reference Center (2020). Fact Sheets: Information for Doctors about the Disorders included in the Expanded Newborn Screening Panel. Newborn Screening Reference Center. Retrieved from https://www.newbornscreening.ph/index.php?option=com_content&view=frontpage&Itemid=56