What Is Hashimoto's Thyroiditis? The Autoimmune Side of an Underactive Thyroid

Hashimoto's thyroiditis is an autoimmune condition. The immune system attacks the thyroid, the small gland at the base of the neck, and over time the thyroid can make less hormone than the body needs. It's a common cause of an underactive thyroid (hypothyroidism) in the U.S. It usually develops slowly, often over years.

What this is / what this is not

What this is: A plain-language explanation of Hashimoto's thyroiditis, who tends to get it, how it's found, and when to talk with a clinician, for Florida adults.

What this is not: A diagnosis or a treatment plan. Not advice to start, stop, or change any medicine or supplement. Not care for anyone outside Florida. Not for emergencies. If you have one, call 911.

Who this may be relevant for

This may be useful if you are a Florida adult who:

• Was told you have thyroid antibodies and want to know what that means
• Has a family history of thyroid disease and wants to understand the risk
• Has symptoms of an underactive thyroid and wants a private conversation with a clinician

It does not diagnose you. Only a licensed clinician, after an evaluation, can say what is going on.

Other names you may hear

The American Thyroid Association (ATA) notes that Hashimoto's thyroiditis is also called chronic lymphocytic thyroiditis or autoimmune thyroiditis. You may also see "Hashimoto's disease." They describe the same condition.

What happens in the thyroid

In Hashimoto's, the immune system makes antibodies against parts of the thyroid. Two you may see on a lab report are thyroid peroxidase (TPO) antibodies and thyroglobulin (Tg) antibodies. White blood cells gather in the gland, and that ongoing inflammation can damage it slowly.

As the damage builds, the thyroid may not keep up. When thyroid hormone runs low, the body's processes can slow down. That is hypothyroidism. Some people also notice the thyroid getting larger. An enlarged thyroid is called a goiter, and it can make the front of the neck look full.

Who is more likely to have it

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says Hashimoto's is much more common in women than in men. Your chances may be higher if you:

• Have a family member with thyroid disease or another autoimmune condition
• Have another autoimmune condition yourself, such as type 1 diabetes, celiac disease, rheumatoid arthritis, or lupus

Having a risk factor doesn't mean you have it. It means the topic is worth raising with a clinician.

How it can change over time

Hashimoto's doesn't look the same for everyone. Some people have antibodies for years while their thyroid still works normally. Others move slowly toward an underactive thyroid. Early on, many people feel nothing at all.

When thyroid hormone does drop, symptoms often come on gradually. They can include tiredness, feeling cold, weight gain, constipation, dry skin, thinning hair, heavier or irregular periods, a slower heart rate, and low mood. These symptoms are common and have many possible causes, which is one reason an evaluation matters.

"My antibodies are high, but my thyroid is normal"

This is a common place to land. Positive thyroid antibodies show the immune system is reacting to the thyroid. They don't, on their own, mean the thyroid is underactive. A clinician looks at antibodies alongside thyroid function tests, your symptoms, and your history.

Our post on thyroid symptoms with a normal TSH explains TSH, free T4, and antibodies in more detail, so we won't repeat it here.

How it's usually diagnosed

A clinician generally starts with your symptoms, history, and an exam of your neck. Blood tests that measure thyroid function and thyroid antibodies help show what's happening. Sometimes an ultrasound of the thyroid is used. Your clinician decides which tests are useful for you.

We can order labs for you, or you can bring recent bloodwork you've already had done.

A note on iodine and supplements

Iodine is needed for thyroid hormone, so supplements that contain it, such as kelp, can seem helpful. NIDDK cautions that people with Hashimoto's may be sensitive to too much iodine. Talk with your clinician before taking any supplement for your thyroid.

What care may involve

Not everyone with Hashimoto's needs treatment. If your thyroid is working normally, a clinician may simply recheck it over time. If it becomes underactive, NIDDK notes that it is usually treated with thyroid hormone replacement. One of our licensed clinicians decides if it fits, based on your evaluation.

Never start, stop, or change a treatment without your prescriber.

If you are pregnant or planning a pregnancy, tell your clinician. Thyroid needs can change during pregnancy.

When to talk to a clinician

Talk to a clinician if:

• You have symptoms of an underactive thyroid that last for weeks
• A lab report showed thyroid antibodies and you want to understand it
• You notice swelling at the front of your neck, or trouble swallowing or breathing

Trouble breathing is an emergency. Call 911.

What a consult may cover

A consult with one of our licensed clinicians starts with conversation, not a menu. It may cover your symptoms, personal and family history, medicines and supplements you take, labs when indicated, and referral to an in-person clinician when needed. This site has no price menu. Fees, and whether a therapy is right for you, are covered in the consult.

Florida telehealth is held to the same standard as an in-person visit. Our consult-first telehealth post explains more, and how a consult works walks through the steps.

Frequently asked questions

Is Hashimoto's the same as hypothyroidism?
No. Hashimoto's is a cause. Hypothyroidism is the result when the thyroid doesn't make enough hormone. You can have Hashimoto's without being hypothyroid.

Can Hashimoto's go away?
It's a long-term condition. Many people live with it well under a clinician's care.

Does it run in families?
It can. Tell your clinician about any family history of thyroid or autoimmune disease.

What if this is an emergency?
Call 911.

A clear next step

This is education, not a treatment plan. A licensed provider decides if care is appropriate.

If you are a Florida adult and want to talk through thyroid antibodies or symptoms in a private consult, request one at Book a consult, or call (727) 577-3558. The form asks only for your name, phone, and email. Keep medical details for the visit.

This journal note is educational. Telehealth for Florida patients only. It does not collect medical details, and it is not for emergencies. Call 911 in a crisis.