How Hashimoto's Disease Is Diagnosed

Hashimoto's disease
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Hashimoto’s disease, also known as Hashimoto's thyroiditis or chronic autoimmune thyroiditis, is a condition in which your body’s immune system begins to attack your thyroid, the butterfly-shaped gland at the base of your neck. This can cause your thyroid to become inflamed and damaged, leading to an underactive thyroid (hypothyroidism). While Hashimoto's disease is the most common cause of hypothyroidism, not all people with the disorder develop hypothyroidism. Hashimoto's is typically diagnosed by a combination of your signs, symptoms, and blood tests.

Self-Checks/At-Home Testing

In many cases of Hashimoto's disease, the thyroid may become enlarged and form a swelling in your neck called a goiter, which you may be able to see or feel. The American Association of Clinical Endocrinologists (AACE) says that up to 15 million Americans may have thyroid issues that haven't been diagnosed, which is why they encourage people to perform a "Thyroid Neck Check" at home.

You can do this simple check to look for any bumps, nodules, or enlargements in your thyroid area. Be aware that though this check can be helpful in terms of early detection, it's not a reliable way to rule out or diagnose a thyroid problem. Many nodules and bumps can't be seen or felt, but if you have any that are large or close to the surface of your skin, you may be able to detect them.

Thyroid Neck Check

If you have other symptoms of Hashimoto's disease or you think you may have a thyroid problem. Here's how to check for possible nodules or enlargements, as recommended by the AACE:

  1. Get a glass of water and a handheld mirror, or stand in front of a mirror.
  2. Tip your head back toward the ceiling, keeping your eyes on your thyroid, which is located in the front of your neck, underneath your voice box and Adam's apple, and above your collarbones.
  3. Take a sip of water and swallow it.
  4. While you're swallowing, watch your thyroid. Do you see any bumps, enlargements, or bulges? If you're not sure, take another sip of water and swallow. Repeat as needed.
  5. Feel your thyroid area. Do you feel any swelling or bumps? Be careful not to confuse your thyroid with your Adam's apple.

If you see or feel any abnormalities, make an appointment to see your doctor. You may have a thyroid disorder or a nodule that needs to be checked.

Labs and Tests

Hashimoto’s is typically diagnosed through a combination of your signs and symptoms, as well as blood tests.

First, your doctor will review your health history, symptoms, and perform a physical exam to check for goiters. It's a good idea to keep a list of your symptoms, as well as any notes about when they occur and what you've been doing when they occur that may give more clues. For instance, if you feel fatigued, is it worse in the morning? At night? After exercising? These details can help your doctor pinpoint the cause of your symptoms more efficiently.

Next, your doctor will likely order blood tests to test your thyroid hormone function and antibodies.

Thyroid Stimulating Hormone (TSH) Test

The standard hormone test looks at your thyroid stimulating hormone (TSH) and this is the one every doctor uses. TSH is made by the pituitary gland in your brain and it works by signaling your thyroid to produce the hormones your body needs.

When your thyroid is under-functioning, your TSH level will usually be elevated because your pituitary gland is trying to prompt your thyroid gland to produce more hormones.

Normal Range

The typical normal range for TSH is 0.5–4.5 or 5.0 milli-international units per liter (mIU/L), but this can vary depending on the laboratory that's doing the testing. However, there's some controversy concerning what's actually normal. Some experts believe that 2.5 or 3.0 mIU/L should be the top end of the range. Others think it should be adjusted to include a higher normal range for elderly adults (6.0 to 8.0 mIU/L) and people with morbid obesity (up to 7.5 mIU/L).

If your TSH level falls under 0.5 mIU/L, this indicates that you have an overactive thyroid (hyperthyroidism). Numbers above the normal range, usually 5.0 mIU/L or higher, show that you may have hypothyroidism. In this case, your doctor will do the test again in a few weeks to make sure the elevation wasn't temporary.

Free Thyroxine Test

Your doctor may do a free thyroxine (free T4) test to check the level of the active thyroid hormone in your blood right away or wait to see if a second TSH test still shows an elevated level before performing the free T4 level.

The normal range for free T4 is 0.8–1.8 nanograms per deciliter (ng/dL).

If you have an elevated TSH level and a low free T4 level, this is consistent with primary hypothyroidism. An elevated TSH and a normal free T4 indicates that you may have subclinical hypothyroidism, a milder form that has fewer or no symptoms.

These two types of hypothyroidism account for more than 95 percent of cases, and most of them are caused by Hashimoto's disease.

Thyroid Peroxidase Antibodies

Another blood test your doctor may order, especially if you have a goiter or subclinical hypothyroidism, looks for antibodies called thyroid peroxidase (TPO) antibodies. These antibodies attack the TPO enzymes found in your thyroid, gradually destroying it. If you have elevated levels, you likely have Hashimoto's disease.

That said, though the majority of people with Hashimoto’s disease—over 90 percent—have elevated TPO antibody levels, this test alone isn’t a sign that you have the condition. Other forms of thyroiditis, such as silent thyroiditis or postpartum thyroiditis, may be responsible. Or you may be one of the more than one in 10 people who have the antibodies but normal TSH and free T4 levels.

Having only the TPO antibodies present with normal TSH and free T4 levels means that your thyroid is functioning normally and you don't have hypothyroidism, but it does mean that you may have Hashimoto's disease. Remember that Hashimoto's doesn't always cause hypothyroidism.

A positive TPO antibody test also doesn't necessarily indicate that you'll develop hypothyroidism in the future, but since it's more likely than it is for someone who tests negative, your doctor may recommend an annual TSH test to keep an eye on your thyroid function.

Imaging

In certain instances, like when you don't have the TPO antibodies in your blood but your doctor still thinks you could have Hashimoto's, he or she may order a thyroid ultrasound. This might be performed at an outpatient center, in your doctor's office, or at the hospital.

An ultrasound provides images of your thyroid using soundwaves so your doctor can see if it's enlarged due to Hashimoto’s disease or to rule out or look more closely at other causes of your symptoms like thyroid nodules. It's a completely painless and non-invasive procedure.

Differential Diagnoses

Almost all instances of primary and subclinical hypothyroidism in the United States are caused by Hashimoto's disease, so if your TSH level is above the normal range, Hashimoto's is most likely the reason. However, occasionally an elevated TSH is an indicator of a different problem, so your doctor will rule out other possible conditions as well.

TSH Resistance

Certain people's bodies are resistant to TSH thanks to a defect in their TSH receptors, causing an elevated TSH level. Some people with this resistance still have normal thyroid function while others are hypothyroid. In hypothyroid patients, there isn't any thyroid swelling like there can be with Hashimoto's and free T4 and T3 (triiodothyronine) levels are usually normal or low.

This condition can be difficult to distinguish from subclinical hypothyroidism, but it helps to consider that TSH resistance is rare and subclinical hypothyroidism is fairly common. TSH resistance due to TSH receptor defects also tends to run in families.

Thyroid Hormone Resistance

Some people have defects in their T3 receptors, causing what's known as a generalized thyroid hormone resistance. Like TSH resistance, this condition is rare. It can cause an elevated TSH level, though some people are within the normal range; free T4 and T3 levels are also typically elevated. Most patients with thyroid hormone resistance have normally functioning thyroids (euthyroid), but some have symptoms of hypothyroidism.

Recovery From Another Illness

If you've recently been hospitalized due to a serious or chronic illness that's not related to your thyroid, it's possible that your TSH level is just temporarily elevated due to the illness.

Examples of these non-thyroidal illnesses include:

  • Gastrointestinal diseases such as gastroesophageal reflux disease (GERD), peptic ulcer disease, and Crohn's disease
  • Pulmonary diseases like chronic obstructive pulmonary disease (COPD), lung cancer, and chronic bronchitis
  • Cardiovascular diseases such as heart failure, coronary heart disease, and peripheral arterial disease
  • Kidney disease
  • Metabolic disorders
  • Inflammatory diseases like rheumatoid arthritis, multiple sclerosis (MS), and systemic lupus erythematosus
  • Heart attack
  • Burns
  • Surgery
  • Trauma
  • Sepsis, an infection in your bloodstream
  • Bone marrow transplantation

If your doctor thinks your elevated TSH level may be due to recovery from a non-thyroidal illness, here's what the plan may look like:

  • For a TSH level that's under 10.0 mIU/L, your doctor will likely test your TSH again in a week or two, as long as you're recovering from your illness. It's unlikely that you'll develop permanent hypothyroidism.
  • For a TSH level that's 10.0 to 20.0 mIU/L, your doctor may put you on thyroid hormone replacement for a time, depending on other factors. You'll also probably have your TSH and free T4 tested in a week or two to check your progress. It's possible that you'll develop permanent hypothyroidism, but most people within this range don't.
  • If your TSH level is 20.0 mIU/L or higher and your free T4 level is low, there's a high chance that you have permanent hypothyroidism and you'll be started on thyroid hormone replacement. However, if your free T4 level is normal, your doctor will repeat the TSH and free T4 levels in a week or two; a treatment plan can be assessed at that time. In the latter case, it's possible that you may not develop permanent hypothyroidism.

In all cases, you'll likely have your TSH and free T4 levels tested again in four to six weeks after you've completely recovered from the illness.

TSH-Secreting Pituitary Adenoma

TSH-secreting pituitary adenomas are actually the cause of some cases of hyperthyroidism, though this is rare. An adenoma is a benign tumor or growth, which means that it's not cancerous. If you have a growth on your pituitary gland that's secreting TSH, this may account for an elevated TSH level.

Unlike in hypothyroidism where your free T4 level is low (primary) or normal (subclinical), with a TSH-secreting pituitary adenoma, your free T4 level is elevated, as is your total T4 and total and free T3. This type of pituitary tumor is fairly rare.

Adrenal Insufficiency

An elevated TSH level can also occur when you have primary adrenal insufficiency, also known as Addison's disease. This disorder occurs when your adrenal glands, which are right above your kidneys, can't produce enough of the hormone cortisol due to damage. In some people, the damaged adrenal glands also can't make enough of the hormone aldosterone. Along with an increased TSH level, adrenal insufficiency can also cause symptoms that are similar to that of hypothyroidism.

Autoimmune Polyendocrine Syndrome Type II

This rare autoimmune disorder, once known as Schmidt syndrome, occurs when you have both Addison's disease and Hashimoto's disease, but it often occurs with Graves' disease (an autoimmune disorder that's a cause of hyperthyroidism), celiac disease, and/or type 1 diabetes as well. Because hypothyroidism is common in this disorder, your TSH levels may be elevated.

There aren't any special tests to diagnose autoimmune polyendocrine syndrome, but your doctor can look for adrenal antibodies in your blood. Since around 50 percent of people with this condition have inherited it, if you have adrenal antibodies, relatives with the disorder, and you also have thyroid disease and/or diabetes but you don't have adrenal insufficiency yet, you're still considered to have autoimmune polyendocrine syndrome type II.

Hashimoto's Encephalopathy

Also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), Hashimoto's encephalopathy (HE) is a rare—and not clearly understood—autoimmune disease that causes swelling in the brain. Though HE doesn't seem to be directly related to thyroid disease, it's associated with Hashimoto's disease.

Studies have shown that around 7 percent of people with HE have hyperthyroidism, 23 percent to 35 percent have subclinical hypothyroidism, and 17 percent to 20 percent have primary hypothyroidism. The rest have normal thyroid function.

In a person with HE, either TPO antibodies or antithyroglobulin antibodies are present. Thyroid levels are also checked, but again, TSH levels can range from low to high. Treatment for HE usually consists of corticosteroids and treating any thyroid issues if they're present.

A Word From Verywell  

Because Hashimoto’s disease tends to progress over your lifetime, if you're diagnosed with it, your doctor will want to test you periodically to make sure you’re on the right dose of medication. Occasionally, your treatment may have to be adjusted. The good news is that most cases of Hashimoto’s disease can be well-controlled through medication, so be sure to take your medication as prescribed even when you begin feeling well. Talk to your doctor if you have any questions about your blood tests or your treatment.

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Article Sources
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