The immune system’s primary role is to protect your body against any bacteria or viruses. So when anything foreign enters your body, your immune system quickly responds by releasing cells to counteract them.
In the case of an autoimmune disease, however, your body cannot distinguish the difference between normal, healthy cells and foreign cells causing an autoimmune response.
This means that your fighter cells will start attacking healthy tissues that would eventually cause medical conditions known as autoimmune diseases, some of which are responsible for hypothyroidism.
Hashimoto’s disease is one of the primary causes of hypothyroidism. This autoimmune disorder causes the immune system to attack the thyroid until it becomes damaged and unable to produce enough thyroid hormones.
Hashimoto’s disease affects 5 in every 100 Americans, making it the most common cause of hypothyroidism in the United States.
Removal of the thyroid
Thyroid problems like thyroid cancer, Graves’ disease and thyroid nodules can sometimes lead to the removal of the entire thyroid gland, which in turn causes hypothyroidism.
This means that you would need to use thyroid medication for the rest of your life. In some cases, only the damaged part of the thyroid will be removed for it to still produce enough thyroid hormones.
Hyperthyroidism treatment
Hyperthyroidism is a condition in which the thyroid gland produces too much thyroid hormone causing several medical conditions.
Medications indicated for hyperthyroidism help reduce thyroid hormone production, but it can sometimes cause the thyroid hormone levels to remain low, especially after treatment with radioactive iodine. This can then result to hypothyroidism.
Congenital hypothyroidism
Congenital hypothyroidism occurs when a child is born with an abnormal thyroid gland. In 80% of cases, the thyroid gland is completely absent, placed abnormally or severely reduced in size.
These conditions are called thyroid dysgenesis because of how the thyroid gland failed to develop or function properly. In other cases, the thyroid gland is normal or slightly enlarged, but it doesn’t produce enough thyroid hormones or none at all.
Congenital hypothyroidism occurs in 1 out of 2,000 babies born and it is more prevalent in females. In the United States, all newborns are tested for hypothyroidism so early treatment can be given.
Radiation therapy
Patients with Graves’ disease, thyroid cancer or goiter nodules are sometimes recommended to undergo radioactive iodine (I-131) therapy to destroy the thyroid gland, which is causing the diseases.
Patients with cancer in the head or neck, lymphoma or Hodgkin’s disease are also treated with radiation therapy that can cause a partial or full impairment of the thyroid function.
Medications
Some medications that are indicated to treat cancer, heart disease and some psychological conditions can lower thyroid hormone production.
The most common drugs that cause hypothyroidism include lithium, amiodarone, interleukin-2 and interferon alpha. These medications usually trigger the condition, especially in patients who have a genetic tendency to autoimmune thyroid disease.
Thyroiditis
Also known as the inflammation of the thyroid gland, thyroiditis is caused by either a viral infection or autoimmune attack. In its first stages, thyroiditis can cause the thyroid gland to dump all of its hormone production into the blood at once causing hyperthyroidism.
But after that, the thyroid gland becomes under-active resulting to hypothyroidism.
Damage to the pituitary gland
Also called the “master gland,” the pituitary gland is responsible for sending the right message telling the thyroid gland how much hormone to make.
So when it is damaged by a tumor, surgery or radiation, it also affects how the thyroid produces thyroid hormones resulting to hypothyroidism.
Iodine problems
Iodine is important in thyroid hormone production, so too much or too little iodine in the body also affects how the thyroid gland produces thyroid hormone.
Rare disorders
In very few instances, some diseases can cause abnormal deposits of substances in the thyroid gland affecting its normal function.
Some examples include sarcoidosis that deposit granulomas and amyloidosis that deposit amyloid protein in the thyroid.