Worldwide, one in 3800 new-borns have Congenital Hypothyroidism (CH) and in India, the statistics are one in 2640! Congenital Hypothyroidism is twice as common in girls as in boys. Fortunately, early diagnosis and treatment can often mean a normal life for babies with CH. The screening test is simple and is available in most hospitals and labs across India.
What is hypothyroidism?
A deficiency of thyroid hormones or a defect in the thyroid hormone function is called hypothyroidism. The thyroid gland, which is located in the neck is responsible for producing two hormones; thyroxine (T4) and triiodothyronine (T3). Thyroid hormones play a critical role in growth and development and maintenance of normal body processes. When the thyroid gland does not produce enough thyroxine, it results in hypothyroidism. Without sufficient thyroid hormones, both physical and mental growth suffers in children.
In adults, various systems of the body are affected. In developed countries, the prevalence of hypothyroidism is about 4-5%. A recent Indian study conducted in 8 major cities found that more than 10% of adults suffer from hypothyroidism.
What is congenital hypothyroidism?
In an infant, hypothyroidism occurs when the baby is not making enough thyroid hormone to grow and develop normally. A deficiency of the thyroid hormone in newborn babies therefore leads to a condition called congenital hypothyroidism. For newborn babies, thyroid hormones are crucial for brain development and overall growth.
Congenital hypothyroidism can cause mental retardation and improper growth. If it is not treated in time, this damage can be irreversible. Eary diagnosis and treatment can give a child born with congenital hypothyroidism a chance to experience normal physical growth and neurological development.
This is why parents must proactively ask for a heel prick test to faciliate early diagnosis and treatment and prevent the possibility of mental retardation.
Can congenital hypothyroidism be prevented?
Unfortunately, not always. However, the risk can be reduced by mothers avoiding radioactive iodine treatment or using iodine as antiseptic. Mothers should also avoid excessive consumption of iodine, based on the doctor’s advice.
How is congenital hypothyroidism caused?
During early pregnancy, as the baby’s organs begin to develop, the thyroid gland, which is at the back of the tongue, moves to the neck. However, this doesn’t happen in some babies. Sometimes, the thyroid gland does not develop at all. Yet another situation is genetic, when the thyroid gland is in the right location, but does not produce thyroxine. All these are instances of congenital hypothyroidism.
Even though congenital hypothyroidism is not always hereditary, family history is taken into account during diagnosis which is often through a routine sonography that may reveal fetal goitre. Also, when a pregnant woman with Graves disease is treated with anti thyroid drugs, this places the fetus at risk for hypothyroidism. Exposure of the mother to radioactive iodine also puts the fetus at risk for CH.
Recognizing the symptoms
A majority of babies born with congenital hypothyroidism do not show any symptoms and look normal at birth, since a small amount of the thyroid hormone T4 is transferred from the mother to the baby during pregnancy. This is why it is crucial to test at birth for early diagnosis and treatment.
Although birth weight and length may be normal, symptoms usually manifest in the form of larger than normal heads. The earliest sign may be the prolongation of physiologic jaundice. Feeding difficulties, particularly sluggishness, a lack of interest, sleepiness and choking spells while nursing may also be present during the first month of their life. Respiratory difficulties because of the large tongue are likely.
Infants with CH cry little, sleep a lot, have poor appetites and are sluggish. Their abdomen is large and umbilical hernia may be present. Body temperature tends to be below normal, often less than 35 degree centigrade and the skin in the extremities may be cold and mottled. They may also have swollen genitals and extremities. Since symptoms appear gradually, there may be a delay in clinical diagnosis.
10% of infants with congenital hypothyroidism also develop other abnormalities such as cardiac, nervous system and vision problems.
What causes congenital hypothyroidism?
Generally, congenital hypothyroidism is not hereditary. It can be because of an abnormal thyroid gland. A few cases can be familial due to errors in thyroid hormone synthesis. A majority of cases show a severe deficiency of thyroid hormone and symptoms appear during the first few weeks after birth. In others with a lesser degree of deficiency, symptoms can take a long time to show up.
What is the best time to screen a baby for congenital hypothyroidism?
Screening should ideally be done within two to four days of birth. If this is not possible, testing must be done before discharge or definitely within 7 days of birth. Neonatal screening for congenital hypothyroidism introduced in 1974 uses a newborn heel prick filter paper blood sample and has become the universal practice worldwide.
A heelprick test is a blood test where blood is drawn from the baby’s heel, to measure the T4 and TSH level. When T4 is low and TSH is high, it indicates hypothyroidism and treatment begins right away.
What about the detection of congenital hypothyroidism before the birth of the child?
Congenital Hypothyroidism is not a hereditary disorder. It is not possible to identify a population of pregnant women who are at high risk for fetal hypothyroidism. Certain pregnancies can be deemed high risk based on family history where a previous infant was born with CH.
However, most cases are diagnosed via routine ultrasonography where a fetal goiter is disclosed.
Also, if a pregnant woman with Graves Disease is treated with anti-thyroid drugs, the fetus is at risk for hypothyroidism. If the mother was exposed to radioactive iodine, this increases the baby’s risk for CH.
What about Treatment?
As soon congenital hypothyroidism is diagnosed in a baby, she is started on thyroid hormone replacement right away. Oral Levothyroxine is the treatment of choice. This is a synthetic thyroid hormone similar to that made by the thyroid gland. This replaces the thyroxine that the baby’s thyroid gland is unable to produce
Levothyroxine is usually given once a day. Most children with CH must take it for the rest of their lives.
The right dosage of this medication is usually well tolerated but too little can cause symptoms of hypothyroidism and delay growth milestones.
Too much can cause diarrhea, restlessness and other symptoms.
Early diagnosis and adequate treatment during the first weeks of life is key, as it can result in normal growth and intelligence. A delay in diagnosis and failure to treat initial hypothyroidism, insufficient treatment and poor compliance in the first 2-3 years of life can cause varying degrees of brain damage. Early diagnosis soon after birth and effective treatment can prevent irreversible brain damage.
Congenital hypothyroidism a hypercritical public health issue
The thyroid hormone is essential for normal brain development. A lack of L-thyroxine can delay this. When replaced early in those with congenital hypothyroidism, and with adequate care and follow up, normal physical growth and neurological development is possible, enabling the baby live a healthy and happy life.
It is important to note that testing thyroid function based only on clinical suspicion, no matter how high the index of suspicion, will miss more than 85% affected infants, leaving them mentally retarded.* Therefore, parents must proactively ask for a heel prick test to facilitate early diagnosis and treatment to prevent the possibility of mental retardation.
Please talk to your doctor for more information about congenital hypothyroidism
References:
- *CONGENITAL HYPOTHYROIDISM: NEED FOR UNIVERSAL NEONATAL SCREENING by Anju Virmani and Anjali Kulkarni – Apollo Medicine, Vol. 2, No. 4, December 2005)
- Desai M. Congenital Hypothyroidism: screening dilemma. Indian Journal of Endocrinology and metabolism 2012;16:S153-5.
- Great Ormond Street Hospital. Congenital Hypothyroidism. Last reviewed by Great Ormond Street Hospital: December 2010. Downloaded from http://www.gosh.nhs.uk/medical-conditions/search-for-medical-conditions/congenital-hypothyroidism/congenital-hypothyroidism-information/ accessed on 23 Aug, 2013.
- Jameson JL,Weetman AP. Disorders of the thyroid gland. In Fauci AS, et al, editors. Harrisions Principles of Internal Medicine. 17th vol 2; McGrawHill, New Delhi: p. 2224-47.
- LaFranchi S. Disorders of the thyroid gland. In Kliegman RM, et al, editors. Nelson Textbook of Pediatrics. 18th vol 2; Saunders Elsevier, New Delhi: p. 2316-32.
As the Member of an Ethics committee that evaluates protocols for human clinical trials, I came across the excellent initiative taken up by GSK to educate the masses on neo-natal screening through their campaign named ACT – Against Congenital Hypothyroidism. The more I read about this, the more I felt a need to write this post. I am also a parent.
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