Iodine deficiency is uncommon in the Western world because iodine is added to salt. Where iodine deficiency is not a problem, the most common cause of hypothyroidism is Hashimoto’s thyroiditis. This is another autoimmune disease, but in this case, the immune system destroys the thyroid gland, producing hypothyroidism. Hashimoto’s thyroiditis tends to run in families so it is likely to have a genetic component. It usually appears after the age of 30 and is more common in females than males.
Hypothyroidism produces many signs and symptoms, as shown in Figure \(\PageIndex{6}\). These may include abnormal weight gain, tiredness, baldness, cold intolerance, and slow heart rate. Hypothyroidism is generally treated with thyroid hormone replacement therapy. This may be needed for the rest of a person’s life. Hypothyroidism in a pregnant woman can have serious adverse consequences for the fetus. During the fetal period, cells of the developing brain are a major target for thyroid hormones, which play a crucial role in brain maturation. When levels of thyroid hormones are too low, the fetus may suffer permanent deficits in cognitive abilities. Deafness is also a potential outcome of hypothyroidism in utero.
Feature: Myth vs. Reality
Thyroid disorders are relatively common, affecting as many as 20 million people in the United States. Because the disorders are common, there are also many common myths about them.
Myth: If you have a thyroid problem, you will know something is wrong because you will have obvious symptoms.
Reality: The majority of people with a thyroid disorder are not aware they have it because the symptoms are often mild, nonspecific, and easy to ignore. Generally, blood tests of thyroid hormone levels are needed to make a conclusive diagnosis.
Myth: If you are diagnosed with a thyroid disorder, you will have to take medication for the rest of your life.
Reality: Whether you need to continue thyroid medication for life depends on the cause of the disorder. For example, some women develop hypothyroidism during pregnancy but no longer need medication after the pregnancy is over and hormone levels return to normal.
Myth: As soon as you start taking thyroid medication, your symptoms will resolve.
Reality: It often takes weeks or even months for thyroid hormone levels to return to normal and symptoms to disappear.
Myth: You can take an over-the-counter iodine supplement to correct hypothyroidism.
Reality: In the United States, where dietary iodine is almost always adequate, iodine deficiency is unlikely to be the cause of hypothyroidism. Therefore, taking supplemental iodine is not likely to correct the problem.
Myth: If thyroid symptoms are mild, you don’t need to take medication.
Reality: Because thyroid hormones are responsible for so many vital body functions, failing to treat even a mild thyroid disorder may lead to a range of other problems, such as osteoporosis or infertility.
Myth: Goiter may be caused by eating “goitrogenic” vegetables, such as broccoli, Brussels sprouts, and spinach.
Reality: Although these foods can interfere with the thyroid’s ability to process iodide, you would have to eat huge amounts of them to cause goiter.
Myth: Thyroid disorders occur only after middle age and only in women.
Reality: Thyroid disorders may occur at any age and in any sex. Hypothyroidism occurs more commonly in older adults, but hyperthyroidism occurs more commonly in younger adults. Although women are more likely to develop thyroid disorders, about 20 percent of cases occur in men.