Hashimoto’s Disease and Hypothyroidism: What to Know About the Link

Here’s what happens when the immune system attacks the thyroid.

Thyroid disease affects 12 percent of Americans, according to the American Thyroid Association. Despite this, there’s still a ton that's unknown about the different causes, experimental treatments, and even comorbidities for hyper- and hypothyroidism. One of the lesser-known causes of thyroid disease is a chronic autoimmune condition called Hashimoto’s disease.

What’s Hashimoto’s Disease?

The thyroid is a small, butterfly-shaped gland located near the throat. Its primary job is to make hormones that control how the body uses energy. The thyroid is essential for regulating weight, temperature, muscle function, and even mental health.

In 1912, Dr. Haraku Hashimoto described "struma lymphomatosa” in patients with goiter (enlarged thyroid) and increased white blood cells in the thyroid. By the 1950s, the condition caused by these antibodies was named after him. Normally, the immune system creates antibodies to fight foreign viruses and bacteria. Sometimes, they attack the body's own cells, tissues, and organs by mistake, which is known as an autoimmune response.

Hashimoto’s, classified as gradual thyroid failure, is triggered when the immune system produces increased anti-thyroid peroxidase (anti-TPO) antibodies that mistakenly attack healthy thyroid gland tissue and follicles.

How Hashimoto’s Differs From Hypothyroidism

Hashimoto’s and hypothyroidism aren’t interchangeable. Hashimoto’s is one of many possible causes of hypothyroidism. Those with Hashimoto’s will probably test positive for anti-TPO antibodies, even if they show no hypothyroidism symptoms. One of the first signs of Hashimoto’s is a goiter. Depending on size, it can cause swelling of the neck and may hinder swallowing and breathing.

Some doctors also note that a thyroid with Hashimoto’s also appears to have lumps, which can be mistaken for thyroid nodules or tumors. This is distinct from someone who has hypothyroidism without Hashimoto's. You may have semi-regular sonograms to check for tumors that need to be biopsied.

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Signs and symptoms resulting from an underactive thyroid (present in either condition) can include:

  • Excessive tiredness (fatigue)
  • Weight gain or difficulty losing weight
  • Constipation
  • Thinning, brittle hair
  • Slower heart rate
  • Joint or muscle pain
  • Loss of color and swelling in the face
  • Feeling cold in a mild climate
  • Disrupted menstrual cycle and fertility
  • Increased menstrual flow and PMS symptoms
  • Decreased concentration and depression

To treat the disease, doctors will prescribe synthetic thyroid hormones to replace what the thyroid can no longer make. At first, you’ll have regular, bi-monthly blood tests to check your levels and adjust your dose as needed. Eventually, testing will reduce to every six months or even once a year once you’ve found the right dose for you.

Synthetic thyroid hormone is affordable, effective at getting normal thyroid hormone levels back to normal, and can improve hypothyroidism symptoms. Most patients with Hashimoto’s will require lifelong treatment. On the other hand, people with hypothyroidism from other causes may be able to improve their condition and wean off the medication. No matter what, you shouldn’t stop taking your medicine without consulting your doctor.

What Causes Hashimoto’s?

Researchers aren’t sure why some people develop autoimmune disorders like Hashimoto’s disease. Experts generally point to a combination of genetics and environment that may precipitate Hashimoto’s in at-risk individuals.

This includes:

  • Missing or damaged X chromosomes in women
  • Changes in other sex hormones (especially for women)
  • Conditions during that affect the fetus
  • Viral infections (i.e. Epstein-Barr virus)
  • Certain medications
  • Exposure to ionizing radiation
  • Eating large amounts of foods that contain animal proteins
  • Excess consumption of iodine (which is involved in thyroid hormone production)

What’s the Prognosis for Those with Hashimoto’s?

When you have the right dose, there should be no side effects. If it’s too low, your TSH remains elevated and your hypothyroidism symptoms could persist. If it’s too high, TSH will become suppressed and you could actually experience symptoms of hyperthyroidism, or have other side effects.

Those with Hashimoto’s disease have an increased risk for:

  1. Developing other autoimmune disorders, including vitiligo, rheumatoid arthritis, Addison disease, type 1 diabetes, multiple sclerosis, and pernicious anemia.
  2. Complications with fertility, pregnancy, and maternal and fetal health. Thyroid disease can be exacerbated during pregnancy, which can be harmful to both the mother and baby. Luckily, synthetic thyroid medicine is safe to take during pregnancy.
  3. High cholesterol and heart disease, due to lower levels of thyroid hormones (from hypothyroidism). Left untreated, it could lead to myxedema coma, in very rare and extreme cases.
  4. Hashimoto encephalopathy (HE), a rare and underdiagnosed syndrome causing brain damage or disease, is associated with increased antithyroid antibody titers. It can cause mental decline, feelings of confusion, and erratic behavior. It can also be accompanied by seizures and muscle spasms, and sometimes coma. As with Hashimoto’s, this is more common in women than men. If you suffer these symptoms out of the blue, it’s worth bringing up to your doctor for more testing and different treatments, like steroids over immunosuppressants.

If you think you might have hypothyroidism or Hashimoto’s (or both), talk to your doctor. That way, they can run the appropriate tests, take an ultrasound to look for goiter or nodules, and/or refer you to an endocrinologist.