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Potential causes of hypothyroidism include:

  • Treatments for hyperthyroidism (e.g., surgery, radioiodine therapy, etc.)
  • Certain kinds of medications (e.g., lithium carbonate, amiodarone, etc.)
  • Infiltrative thyroid diseases, which are characterized by a gradual increase in the size of the thyroid
  • Certain types of cancer treatment can also result in hypothyroidism (e.g., external-beam radiation therapy to treat Hodgkin’s disease or thyroid cancer surgery)
  • A severe iodine deficiency (iodine is necessary for thyroid hormone production)

What Causes Certain Types of Underactive Thyroid?

Of course, what exactly causes the thyroid to underperform can affect the type of hypothyroidism someone develops.

Primary Congenital Hypothyroidism

Primary congenital hypothyroidism may occur due to thyroid dysgenesis, or when a baby is born without a thyroid or the thyroid itself is just too small to work properly. This classification also refers to when the baby’s thyroid does not function correctly or when the thyroid develops in an abnormal location.

Other issues that can cause primary congenital hypothyroidism include an enlarged thyroid gland or a normal-sized gland that either does not produce hormones or produces too few. Experts classify these issues as thyroid dyshormonogenesis.

If the pituitary gland is not stimulating the thyroid to produce hormones, this issue is classified as central hypothyroidism.

In short, potential causes/classifications of primary congenital hypothyroidism include:

  • Thyroid dysgenesis
  • Thyroid dyshormonogenesis
  • Central (pituitary) hypothyroidism

Central Hypothyroidism

The pituitary gland is a small gland located inside the brain, close to the hypothalamus; it is responsible for regulating a wide range of bodily functions, including that of most of the body’s endocrine system, or the system associated with providing the body certain hormones. Together with the hypothalamus, the pituitary gland regulates the thyroid gland.

Central hypothyroidism can result from pituitary disease or due to an inadequate amount of thyrotropin, the thyroid-stimulating hormone that the pituitary gland secretes. Thyrotropin stimulates the thyroid, signaling it to produce both T4 and T3.

Central hypothyroidism may also be the result of a disorder of the hypothalamus, pituitary, or hypothalamic-pituitary portal circulation, which causes a deficiency of hypothalamic-pituitary hormones, which are responsible for many functions, including stimulating the thyroid gland.

Hashimoto’s Thyroiditis

Medically 3D illustration showing antibodies attacking thyroid gland of a man. Hashimoto's thyroiditis, also known as Hashimoto’s disease or even chronic lymphocytic thyroiditis
Antibodies produced by the immune system attack the thyroid, leading to inflammation and hypothyroidism. (Credit: Axel_Kock/Shutterstock.com)

Hashimoto’s thyroiditis—also known as Hashimoto’s disease or even chronic lymphocytic thyroiditis—is the most common culprit behind hypothyroidism. It is an inherited disorder in which the immune system attacks a healthy thyroid gland, resulting in inflammation. This inflammation inhibits the gland’s ability to produce an adequate number of thyroid hormones.

Potential causes of Hashimoto’s thyroiditis include:

  • Thyroid surgery
  • Certain kinds of medications
  • Radiation treatments performed on the thyroid
  • Damage to the pituitary gland

Risk factors associated with developing Hashimoto’s disease include:

  • Leaky gut syndrome (increased intestinal permeability)
  • Hormonal imbalances
  • Infections
  • Food sensitivities
  • Exposure to toxins
  • Nutrient deficiencies

Atrophic Thyroiditis

Atrophic thyroiditis is a less common form of hypothyroidism that refers to the end stages of autoimmune primary hypothyroidism and is characterized by the thyroid gland shrinking.

Postpartum Underactive Thyroid

Postpartum hypothyroidism occurs following pregnancy, typically presenting within the first six months after giving birth.

Postpartum hypothyroidism is rare, only affecting about 5 percent of cisgender women who have given birth. However, women who are at a greater risk of experiencing this form of hypothyroidism are those who have:

  • type 1 diabetes,
  • a personal and/or a family history of thyroid dysfunction, and/or
  • thyroid-specific antibodies.

Some experts believe that women who develop postpartum hypothyroidism actually have an underlying asymptomatic (symptomless) autoimmune thyroid condition like Hashimoto’s disease.

Risk Factors

There are certain risk factors experts associate with the development of hypothyroidism, including:

  • Being a senior citizen (60 years or older)
  • Genetic disposition to an autoimmune disease and/or a thyroid disease
  • Previously experiencing thyroid issues or having thyroid surgery
  • Having some kind of autoimmune disease (e.g., rheumatoid arthritis, multiple sclerosis (MS), type 1 diabetes, etc.)
  • Sex
  • Turner syndrome (TS), a genetic disorder affecting only cisgender females in which one of the X chromosomes is partially or completely missing
  • A recent pregnancy
  • Other pre-existing health problems (e.g., pernicious anemia, Sjögren’s syndrome or lupus, etc.)

FAQ

Can stress cause thyroid problems?

Although there is currently no proof that stress directly causes the onset of thyroid problems, stress can exacerbate thyroid issues that already exist.

How does hypothyroidism affect the body?

Hypothyroidism is characterized by the slowing of body functions like metabolism. The neuromuscular (nerve and muscle) symptoms associated with this disorder include a slowing of speech, thought and action as well as slowed reflexes.

In addition, individuals who have hypothyroidism may experience:

  • Weakness
  • Muscle aches
  • Overall fatigue
  • Sleepiness
  • High cholesterol

Although rare, when treatment is not sought for this disorder, a complication known as myxedema coma (aka, myxedema crisis) may result; it is a medical emergency that requires immediate attention.

Can hypothyroidism be cured?

While some doctors do believe that lifestyle changes can reverse certain forms of hypothyroid disorder (e.g., Hashimoto’s disease), there is currently no known cure for hypothyroidism. Nonetheless, medication can help patients effectively manage their symptoms.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.


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