What Is Hypothyroidism?
When the thyroid gland does not produce enough thyroxine or thyroid hormone to meet the body's basic requirement, the condition is known as an underactive thyroid or hypothyroidism. This condition makes a person gain weight, feel tired, and unable to tolerate cold temperatures.
What Is ADHD?
Attention deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that occurs in children and can last until adulthood. The condition causes a person to have trouble paying attention. They become overly active and are unable to control impulsive behavior. ADHD causes low self-esteem, work or school difficulty, and troubled relationships.
Attention deficit/hyperactivity disorder in children is mainly caused by the following:
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Use of alcohol and tobacco during pregnancy.
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Brain injury.
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Low birth weight.
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Premature delivery.
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Exposure to various environmental risks during pregnancy, such as lead.
How Is Hypothyroidism in Pregnant Mothers Linked to ADHD in Their Children?
Thyroid hormone plays a vital role in normal neurodevelopment in infants during the early phase of pregnancy. The baby is entirely dependent on their mother for thyroid hormone (thyroxine), which is supplied to them through the placenta, as they cannot make thyroid hormone during the initial phase of pregnancy (up to 12 to 14th week of gestation).
Therefore, overt or severe hypothyroidism in mothers during pregnancy can have an adverse effect on the neurodevelopment of babies, and they may have a low IQ (intelligence quotient), ADHD, or autism spectrum disorder (ASD). However, various other studies show conflicting results, and researchers are still unsure if the treatment of a pregnant mother with levothyroxine for subclinical or mild hypothyroidism can benefit their children's neurodevelopmental outcome.
Therefore, the debate is still going on whether or not thyroid dysfunction in pregnant women should be screened and treated.
What Are the Causes of Hypothyroidism in Pregnant Mothers?
Hypothyroidism (overt or subclinical) can occur in pregnancy due to iodine deficiency, mainly caused due to an autoimmune disorder called Hashimoto's thyroiditis. Women diagnosed with subclinical hypothyroidism before pregnancy can develop hypothyroidism post-pregnancy, which can adversely affect the baby's neurodevelopmental health.
What Are the Clinical Features of Hypothyroidism During Pregnancy?
Hypothyroidism is challenging to identify during the early stages of pregnancy as it presents common pregnancy symptoms. These symptoms are as follows:
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Tiredness or fatigue.
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Weight gain.
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Feeling cold.
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Dry skin and hair.
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Constipation.
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Depression.
In addition, some cases of mild hypothyroidism sometimes present no symptoms.
In What Cases Is a Woman Screened for Thyroid During Pregnancy?
Women must be screened for thyroid during pregnancy in the following cases:
1. If they have a family history of thyroid disease.2. If a person lives in an area with mild to moderate iodine insufficiency.3. Pregnant women should also be screened if they present a personal history of the following medical conditions:
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Type 1 diabetes.
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Goiter.
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Autoimmune disorder.
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Thyroid peroxidase (TPO) antibodies.
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History of multiple pregnancies.
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Past history of thyroid surgery.
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Age 30 years or above.
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Head and neck irradiation.
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Use lithium, amiodarone, or any recent administration of iodinated radiologic contrast agents.
What Are the Complications Associated With Hypothyroidism During Pregnancy?
Hypothyroidism can cause complications both in the fetus and the mother during pregnancy. These include;
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Maternal complications include gestational diabetes, postpartum hemorrhage, gestational hypertension, and abruption placenta.
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Fetal complications include premature births, abortions, low birth weights, and stillbirths. Hypothyroidism also affects the neurodevelopment of the fetus. Therefore, children born to mothers with untreated subclinical hypothyroidism are more at risk of developing learning disabilities, have low IQ, and are more likely to have attention deficit/hyperactivity disorder (ADHD).
How Is Hypothyroidism Diagnosed in Pregnant Women?
Hypothyroidism is diagnosed in pregnancy based on free T4 and trimester-specific TSH levels. For non-pregnant women, the reference range of thyroid hormone is 0.5 to 4.5m U/L.
According to ATA (American Thyroid Association), the reference range for first-trimester pregnancy is 0.1 to 0.4 mU/L. These levels return to the normal non-pregnant range in the second and third trimesters. Also, due to an increase in thyroid-binding globulin (TBG), the total T4 level is elevated; therefore, measurement of free T4 is also recommended in pregnant women. In addition, ATA also suggests that if TSH (thyroid stimulating hormone) is more than 2.5 in pregnant women, thyroid peroxidase (TPO) antibodies should also be tested. This testing is recommended mainly because women with anti-TPO positive and subclinical hypothyroidism are more at risk of developing adverse pregnancy outcomes.
How Can Hypothyroidism Be Treated During Pregnancy?
Levothyroxine is the treatment option for hypothyroidism during pregnancy, with a goal of serum TSH of less than 2.5 mlU/L. Women receiving treatment for hypothyroidism during pregnancy must be screened for serum TSH at four to six weeks of pregnancy. Also, on a stable medication dose, they should be later screened every four to six weeks up to 20 weeks of pregnancy, then at 24 to 28th-week gestation, and 32 to 34th-week gestation.
What Is the Prevalence of Hypothyroidism in Pregnant Women?
Overt or subclinical hypothyroidism is a very common condition during pregnancy. In subclinical hypothyroidism, TSH is increased, and T4 levels are normal, whereas in overt hypothyroidism, TSH is increased, and free T4 levels are decreased. The prevalence rate of hypothyroidism and undiagnosed hypothyroidism in pregnancy is about two to three percent, and 3 to 15 percent, respectively.
Conclusion
Thyroid dysfunction is a common endocrinological disorder that occurs during pregnancy. The condition can cause fetal and maternal complications during pregnancy due to the physiological status of the thyroid gland and the inability to adapt to these changes. In addition, untreated hypothyroidism can cause difficulty in conceiving and also cause various complications in the pregnancy itself. Therefore, regular screening for hypothyroidism should be done in pregnant women to avoid any adverse outcomes, such as mental health disorders like ADHD in children. Also, timely treatment should be availed if a person is diagnosed with subclinical hypothyroidism.
