How Hashimoto's Disease Is Diagnosed

Tests for Hashimoto’s disease, also known as Hashimoto's thyroiditis or chronic autoimmune thyroiditis, are used to identify a condition in which your body’s immune system begins to attack your thyroid, the butterfly-shaped gland at the base of your neck.

Apart from iodine deficiency, it is the most common cause of thyroid damage and inflammation that leads to an underactive thyroid (hypothyroidism). Not all people with the disorder develop hypothyroidism. Hashimoto's is typically diagnosed by a combination of your signs, symptoms, and blood tests.

This article explains tests for Hashimoto's disease and how it is diagnosed.

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 see or feel. It's a common symptom of Hashimoto's disease.

You can do a 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 thyroid 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.

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 healthcare provider. 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. Your healthcare provider 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.

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

Thyroid Stimulating Hormone (TSH) Test

This standard hormone test looks at your thyroid stimulating hormone (TSH). 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 isn't functioning well, 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 studies suggest "normal" levels within the range are still associated with higher risk of thyroid disease. Other experts advocate for different range values specific to older adults, people diagnosed with obesity, and other situations.

If your numbers are outside the normal range, your healthcare provider will do the test again in a few weeks to make sure the elevation wasn't temporary.

Free Thyroxine Test

Your healthcare provider may do a free thyroxine (free T4) test to check the level of the 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).

Thyroid Peroxidase Antibodies

Another blood test your healthcare provider 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.

The majority of people with Hashimoto’s disease (more than 90%) have elevated TPO antibody levels, but 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.

What Do the Results Mean?

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.

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

You also may see a negative result suggesting there's no autoimmune disorder, or a positive test for another condition (like Graves' disease) on the basis of specific TPO antibodies.

Imaging

In certain instances, your provider may order a thyroid ultrasound. This might be performed at an outpatient center, in your healthcare provider's office, or at the hospital.

An ultrasound provides images of your thyroid using soundwaves so your healthcare provider can see structural changes that may be due to Hashimoto’s disease or to identify thyroid nodules or other conditions. It's a painless and non-invasive procedure.

Differential Diagnoses

An elevated TSH level can be caused by another condition. Your healthcare provider may need to consider these possibilities.

TSH Resistance

Some people are resistant to TSH due 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 as 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 people 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 chronic obstructive pulmonary disease (COPD) and metabolic disorders. You also may experience temporary TSH changes with trauma recovery (burns, surgery) or with infection such as sepsis, which spreads in your bloodstream.

Older studies suggest a possible relationship between temporary TSH changes and:

• Gastrointestinal diseases such as gastroesophageal reflux disease (GERD), peptic ulcer disease, and Crohn's disease
• Pulmonary diseases that include lung cancer and chronic bronchitis
• Cardiovascular diseases such as heart failure, coronary heart disease, and peripheral arterial disease
• Kidney disease
• Inflammatory diseases like rheumatoid arthritis, multiple sclerosis (MS), and systemic lupus erythematosus
• Heart attack
• Bone marrow transplant

If your healthcare provider 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 healthcare provider 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 healthcare provider 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 hypothyroidism and you'll be started on thyroid hormone replacement. However, if your free T4 level is normal, your healthcare provider 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.

Adrenal Insufficiency

An elevated TSH level can also occur when you have primary adrenal insufficiency. Sometimes 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 healthcare provider can look for adrenal antibodies in your blood due to the strong genetic origins.

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.

In a person with HE, TSH levels can range from low to high. Treatment for HE usually consists of corticosteroids and treating any thyroid issues if they're present.

Summary

Hashimoto’s disease is the most common cause of hypothyroidism, apart from iodine deficiency. It tends to progress over your lifetime. You may experience symptoms and your healthcare provider will want to test you periodically to ensure you’re on the right dose of medication.

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 healthcare provider if you have any questions about your blood tests or treatment. Occasionally, your treatment may have to be adjusted.