What causes hypothyroidism

Michael Rosenberg
Michael Rosenberg

Specializes in translating complex information into readable, engaging content. Michael@top10us.com

Causes of hypothyroidism

There are two major causes of hypothyroidism: primary and secondary. In primary causes, the thyroid is affected directly, and it reduces the level of thyroid hormone production. On the other hand, in the secondary causes, the failure of the pituitary gland occurs, and these glands cannot send thyroid-stimulating hormone to the thyroid to fix the hormone balance. The primary causes are very common and one of the most common causes is an autoimmune condition that is known as Hashimoto’s disease. It is also known as Hashimoto’s thyroiditis or chronic lymphocytic thyroiditis. It is a hereditary disease, and it may be caused due to bacterial and viral infections, radiation exposure, and stress.

Other primary causes can be

  • Inflammation of the thyroid or thyroiditis
  • Hereditary conditions
  • Removal of the thyroid by surgery and radiations
  • Due to the deficiency of iodine

Causes of hypothyroidism in pregnancy

Women suffer from Hashimoto’s disease due to hypothyroidism during pregnancy. This disease causes the immune system of the body to attack the thyroid gland and damage it. Due to the damage of the thyroid, there is no release and production of the thyroid hormone that leads to muscle cramps and body pain in pregnant women. It also affects the baby’s development. Thyroid hormone is very important for the development of the nervous system and brain of the baby.

The treatment of hyperthyroidism

Due to the overproduction of thyroid, people go for its treatment. They are treating hyperthyroidism with antithyroid medicines or radioactive iodine. The main purpose of this treatment is to stabilize the making of thyroid hormone but sometimes it may lead to hypothyroidism. Hyperthyroidism lowers the creation of a thyroid hormone that may lead to permanent hypothyroidism.

Surgery and radiation of thyroid glands

During the surgery, removal of a large portion of the thyroid gland can reduce or stop the production of thyroid hormone. If the whole part of the thyroid gland is taken out, then the patient definitely would suffer from hypothyroidism.

In the case of thyroid cancer or Graves’s disease, the patient is treated with radioactive iodine and the thyroid gland is destroyed by these radiations. 

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Medicines and use of little or too much iodine

The medicines that are used to treat psychiatric conditions, cancer, and heart diseases such as interferon-alpha, amiodarone, interleukin-2, tyrosine kinase inhibitors, and lithium diminish the production of thyroid hormone and cause hypothyroidism.

The human body does not produce iodine. It is taken along with the food. Best iodine source foods are eggs, saltwater fish, dairy products, seaweed, and shellfish. Iodine is necessary to the thyroid gland for the production of thyroid hormone. The right amount of iodine is required for the thyroid gland to function properly but lack or excess of iodine can cause hypothyroidism.

Abnormalities in the pituitary gland

Abnormalities in the pituitary gland can cause hypothyroidism. The pituitary gland produces thyroid-activating hormone that controls the thyroid glands for the production and release of thyroid hormone. If the pituitary gland does not function properly, the production of thyroid hormone stops or produces less than its requirement. The pituitary gland may get damaged due to Sheehan’s syndrome.


Thyroiditis is the swelling of the thyroid gland. It is caused by a bacterial or viral infection, an autoimmune attack, or during pregnancy. Due to this inflammation, the thyroid hormone dumps all the stored thyroid hormone into the blood at once which leads to hyperthyroidism right away, but it becomes underactive and after 1 to 2 months it causes hypothyroidism.

Congenital hypothyroidism

Some babies are born without or half part of the thyroid gland or some have parts of the thyroid gland placed in the wrong place. Due to abnormal development, these babies suffer from hypothyroidism from the very first day of their birth. In some babies, congenital hypothyroidism can be inherited but these babies appear normal at the time of birth and such babies suffer from insufficient mental growth and physical problems. In the US, most newborns are screened for hypothyroidism.  

Nodules thyroids and disorder of the hypothalamus

Unusual growth of thyroid cells forms lumps in the thyroid gland and this condition is known as nodules thyroids. Due to unnecessary growth, the production and release of thyroid hormone get disturbed or stopped causing hypothyroidism. Thyroid nodules can be formed because of radiation exposure, age, and family history. The chances of nodules in women are more than in men.  

It is a rare form of hypothyroidism. It is related to the functioning of the hypothalamus. If the hypothalamus fails to produce thyroid regulating hormone, then it can affect the production and release of thyroid-stimulating hormone in the pituitary gland and leads to hypothyroidism.

Postpartum thyroiditis

Postpartum thyroiditis can happen to women after the baby’s birth. Almost 3 women out of 100 face this problem. At first, it makes the thyroid overactive, and an excess amount of thyroid hormone is released into the blood and it leads to hyperthyroidism. But with time, the production of thyroid hormone stops, and it causes hypothyroidism.

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Hypothyroidism, Hyperthyroidism and Thyroid Tests


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