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Hypothyroidism Causes

Hypothyroidism: Causes

Top Causes

1. Hashimoto’s disease

Hashimoto’s disease or Hashimoto’s Thyroiditis is referred to the condition of enlarged or inflamed thyroid gland (or goiter). Inflammation of thyroid glands results in lesser production of thyroid hormones causing hypothyroidism. It is an autoimmune disease in which antibodies produced in the body attack the thyroid glands, thus causing inflammation. Blood samples of patients suffering from enlarged thyroid revealed the presence of a larger number of antibodies (anti- thyroid peroxidase) produced in response to the enzyme thyroid peroxidase. The exact reason behind the abnormal production of antibodies is yet to be confirmed. This is one of the reasons that Hashimoto’s disease is often genetically inherited. Autoimmune diseases are often caused by more than one factor; often a bacterium or virus may be a triggering factor for this disorder.

2. Treatment of hyperthyroidism

Radioactive iodine and anti-thyroid medications are often administered to patients suffering from hyperthyroidism (excess production of thyroid hormone) or Grave’s disease to balance the normal thyroid levels. Prolonged treatment of hyperthyroidism often leads towards permanent hypothyroidism. The thyroid glands become under active due to these hyperthyroidism medications and start producing very low amounts of thyroid hormones inducing the symptoms of hypothyroidism. A combination of radioactive iodine and anti–thyroid medications are administered to minimize the negative effects of radioactive iodine. However, those who underwent radioiodine therapy should monitor their thyroid hormone levels for few years to check the chances of developing hypothyroidism.

3. Iodine deficiency

Iodine is the main constituent of Thyroxin (T4) hormone, and acute iodine deficiency is one of the prime causes of hypothyroidism. Researches have revealed that most cases of hypothyroidism across the globe arise due to iodine deficiency. Nations following a diet poor in iodine content report maximum cases of hypothyroidism. Hypothyroidism due to iodine deficiency is mainly observed in people residing in hilly areas, whereas it is least observed in people residing in coastal areas. This is because seafood and seaweeds (kelp, Kombu, and bladder wrack) are rich in iodine and people following a seafood diet can prevent this disorder. US have successfully eliminated this disease introducing iodine fortified table salt and bread.

4. Congenital factors

Hypothyroidism can arise from certain congenital factors as well. Babies born with a defective and under developed thyroid gland, or without any thyroid gland are likely to suffer from hypothyroidism. This condition is observed in one out of 3000-4000 babies in US, Europe, Australia, and Japan. The reasons for such deformities are yet to be confirmed but this condition may be inherited. Mutation of certain genes is mainly responsible for congenital hypothyroidism. Babies born with a defective thyroid or without thyroid glands appear to be normal with no symptoms of hypothyroidism. This is the reason that thyroid screening of the newborns has become mandatory in most states of US.

5. Abnormality in the pituitary gland

The pituitary gland, located in the brain is known as the “master gland” of our endocrine system, as it regulates the functions of other endocrinal glands including the thyroid. Therefore, any abnormality in the pituitary gland can cause hypothyroidism. Dysfunction of the pituitary gland due to injury and trauma can affect the production of thyroid hormones. Often a tumor in the pituitary gland (mostly benign in nature) or a brain surgery can seriously affect the performance of the thyroid glands. Sometimes the pituitary gland and hypothalamus may fail to send right signals to the thyroid glands giving rise to hypothyroidism.

6. Pregnancy

Women may develop hypothyroidism during and after pregnancy. Hypothyroidism during pregnancy is often related to Hashimoto’s disease or autoimmune disease, as the antibodies produced in the body directly attack the thyroid glands resulting in low production of thyroid hormones. Often, existing hypothyroidism condition is manifested during pregnancy. Hypothyroidism during pregnancy calls for a serious medical attention to avoid complications like miscarriage, pre eclampsia, and anemia. This disorder often accounts for low birth weight of newborns and delivery of stillborn babies. Pregnant women should go for blood tests to evaluate the thyroid hormone levels to be at the safe side. Doctors often prescribe iodine rich diet during pregnancy to maintain normal functioning of the thyroid glands.

7. Medications

Medications can also cause hypothyroidism. Lithium, a drug widely used to treat psychiatric conditions, can result in low production of thyroid hormones. Drugs like Methimazole and Propylthouracil (PTU), which are used to treat hyperactive thyroid glands often lead to hypothyroidism. Prolonged usage of the drug Amiodarone (Cordarone) to treat abnormal heartbeat can lead to hypothyroidism. Chemotherapy administered to various cancer patients can impair normal functioning of the thyroid glands. People taking anti-depressants can also suffer from this condition. Drugs that are used to treat epilepsy, multiple sclerosis, and hepatitis are often responsible for hypothyroidism. The increased production of antibodies by some of these drugs induces this disorder.

8. Radiation therapy

Intensity Modulated Radiation Therapy (IMRT) coupled with taxane based chemotherapy administered to patients suffering from locally advanced stages of head and neck cancers (LAHNC) can lead to hypothyroidism. Radiation adversely affects the small blood vessels, which gradually stops circulation resulting in under performance of the thyroid glands. Radiation therapy also includes the use of radioactive iodine to treat hyperthyroidism. The thyroid glands often become inactive due to this treatment producing very low levels of thyroid hormones. Radiation therapy therefore is administered in controlled measures as the risk of damaging the thyroid glands always prevails. Thyroid hormone levels should be monitored regularly while administering radiation therapy.

9. Surgery of thyroid gland

Surgery of the thyroid gland is another cause of hypothyroidism. Thyroid gland surgery is required mainly in cases of thyroid cancer. The doctor may remove a part (partial thyroidectomy) or the whole (total thyroidectomy) thyroid gland depending upon the condition. Surgical intervention is also demanded to remove nodules or cysts and benign tumors from thyroid glands in case of thyrotoxicosis (dangerously hyperactive thyroid gland) or to reduce thyroid inflammation (non-toxic goiter). Surgery of thyroid gland may be carried out in pregnant women in case the anti-thyroid drugs fail to check hyperthyroidism. Children may also need to undergo thyroid gland surgery if the parents wish to avoid radioactive iodine therapy.

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