Thyroid Hormones and Antibodies: Diagnosing Hashimoto’s Disease

Thyroid Hormones and Antibodies: Diagnosing Hashimoto’s Disease

Diagnosing autoimmune disorders can be tricky, time-consuming, and expensive. Many people sense that something isn't right with their health, yet are told everything is ok.

It can be a frustrating and scary thing. I've been experiencing a lot of strange symptoms, seeing doctors, and going through countless lab tests for about a year now. For the most part, I've been told that I'm fine and that tests are normal.

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I was referred to a rheumatologist after a positive ANA at my regular doctor's office, indicating possible autoimmunity. The rheumatologist tested for a million different things and found nothing. Even the ANA came out negative this time. I knew something was wrong but there was zero data to back it up. I wanted a second opinion.

What does it mean to test positive for thyroid antibodies?

This question was not even a blip on my radar until recently. After several months of wait time, I finally got in with a second rheumatologist last week. I almost didn't go because I'd been feeling slightly better and I didn't really want to drive into Nashville. Luckily, I did go and this doctor came up with an answer.

My new doctor decided to test my thyroid antibodies which I thought was a waste of time because my thyroid hormone tests were all normal. His office called me a couple of days later saying that my thyroid antibodies were extremely high. I was diagnosed with Hashimoto's Thyroiditis (or Hashimoto's Disease). This was quite a shock but such a relief at the same time. I get into more details about thyroid antibodies below. 

What is Hashimoto's Thyroiditis?

Hashimoto's Thyroiditis is an autoimmune thyroid disorder where the body attacks the thyroid gland causing damage over time. It is the most common cause of hypothyroidism in the US and is believed to have a pretty strong hereditary component. I don't know of anyone in my family that has a thyroid disorder but it's possible they just haven't been diagnosed. 

Like many autoimmune disorders, it affects a lot more women than men (about 10:1) and most often appears between ages 30 and 50. 

Thyroid Hormones

Thyroid hormones play a big role in regulating weight, body temperature, mood, muscle strength, and energy. These are often used to detect thyroid issues. The main hormones secreted by the thyroid are thyroxine (T4) and tri-iodothyronine (T3). 

If you're wondering about your own thyroid hormone levels you can get an at-home thyroid test kit. You can save 15% at EverlyWell by using the code RESULTS15.

Thyroxine (T4)

Thyroxine contains 4 atoms of iodine and is the major hormone secreted by the thyroid gland. Abnormal levels of T4 (too high or too low) can indicate thyroid issues.

Two types are T4 are tested (Bound T4, which attaches to certain proteins preventing it from entering body tissues and Free T4 (FT4), which enters body tissues as needed). A total T4 test measures both of these.

Free T4 is considered the most important measure of thyroid function (rather than bound or total). High free T4 indicates hyperthyroidism and low free T4 indicates hypothyroidism. 

T4 Normal range

.8-1.8 ng/dL (this is according to the lab used by my doctor) or 5 – 11 µg/dL according to The Cleveland Clinic. In case you're wondering the difference between µg/dL and ng/dL, here it is: 1 ng/uL = 100 ug/dL; 1 ug/dL = 0.01 ng/uL.

Thyroid-stimulating Hormone (TSH)

This is released by the pituitary gland and regulates thyroid function. It's also very commonly tested to determine if your thyroid is functioning normally.

The amount of TSH released by the pituitary gland is in response to the amount of T3 and T4 circulating in your system.  

TSH Normal Range

.35-5.5 mIU/L

This is according to the lab used by my doctor. The American Thyroid Association says between 0.4-0.5 mU/L on the lower end and 4-5.5 mU/L on the upper end of the range. Though there is some debate about this range as this article discusses. 

TSH and FT4

If TSH level is high and FT4 is low this suggests an underactive thyroid (hypothyroidism).

If TSH level is low and FT4 is high this suggests an overactive thyroid (hyperthyroidism).

Tri-iodothyronine (T3)

This hormone regulates metabolism and is created by the removal of an iodine atom from T4. This is generally only tested if hyperthyroidism is suspected and can help make a diagnosis, especially if T4 is normal. 

T3 Normal Range

75 to 195 ng/dL (1.1 to 3 nmol/L), according to this

Hypothyroidism: Low TSH and high T4.

Hypothyroidism Primary: High TSH and Low T4

Hypothyroidism Secondary: Low TSH and Low T4

The downside to relying only on thyroid hormone tests

Oftentimes (at least from what I've observed/read/heard), if thyroid hormone tests are normal, no further testing is done. However, having normal thyroid tests doesn't necessarily mean you don't have a thyroid issue. 

I'm grateful that my current doctor thought to take things a step further and test for thyroid antibodies because I would otherwise have no idea I had a thyroid issue for probably years.

My understanding is that often nothing is done (because nothing is detected) until years, even decades later when the thyroid is destroyed, thyroid hormone levels are completely out of whack, and symptoms are much more obvious.

Thyroid antibodies are much more sensitive tests and can help you to be aware of the issue and attempt to do something about it sooner. 

What are thyroid antibodies?

Thyroid antibodies are substances produced by cells called lymphocytes when the body's immune system perceives something to be a threat (this would normally happen with bacteria or viruses).

Unfortunately, the antibodies mistake the thyroid for a foreign invader, so they attack it, leading to chronic inflammation (thyroiditis) and damage to the thyroid.

According to The Office on Women's Health, "More than one in 10 people have the antibodies but have normal thyroid function."

The two most common thyroid antibodies tested are thyroglobulin antibodies (TgAb) and thyroperoxidase antibodies (TPOab).

These are used as markers for autoimmune thyroid disease. High levels of these antibodies can indicate Hashimoto's (hypothyroidism) or Graves' Disease (hyperthyroidism). 

Thyroid peroxidase/thyroperoxidase antibodies (TPOab)

Thyroid peroxidase (TPO) is an enzyme normally found in the thyroid gland and it plays a role in thyroid hormone production. Tests that detect TPO antibody levels are the most sensitive available for detecting autoimmune thyroid disease.

The reference range for TPO is less than 9 IU/mL (according to the lab used by my doctor). Cleveland Clinic says 0.0 - 5.0 IU/mL is a "desireable level." Mine was 624! This is typical of Hashimoto's and is often seen in Graves' disease as well. 

If you're wanting to know your TPO levels, you can ask your doctor or get an at-home thyroid test kit. Save 15% at EverlyWell by using the code RESULTS15.

Moderately increased levels of thyroperoxidase (TPO) antibodies may be found in patients with nonthyroid autoimmune diseases like pernicious anemia, type I diabetes, or other disorders that activate the immune system.

Thyroglobulin Antibodies (TGAb)

These are proteins produced by normal thyroid cells and by thyroid cancer cells. There's some correlation between TGAb, Hashimoto's and thyroid cancer, though it's a little confusing to me. My doctor insists that with my high levels of TGAb, it is definitely Hashimoto's and not thyroid cancer.

As far as thyroid cancer goes, my understanding is that because Tg is thyroid-specific (ie, the thyroid produces it), it is used to test for recurrence of thyroid cancer after the thyroid is removed. Serum Tg concentrations should be zero, or very low, after the thyroid gland is removed in the case of thyroid cancer. You can read more about Hashimoto's and TGAb in relation to thyroid cancer here, here, and here

The reference range for TGAb

(according to the lab report I received) is less than 1 ng/ml. This says less than 4 IU/ml. Other sources like this one that says it should be less than 39 IU/ml. Mine was 533 so either way, pretty high. 

Thyroid-Stimulating hormone receptor (TSHR) (TSAbs)

This is a marker for Graves' Disease. This article/study published in The Journal of Immunology, goes really in depth on the topic of  TSHR in relation to Graves' disease. 

What are the signs and symptoms of thyroiditis?

Often, people go many years before they show any outward signs of thyroiditis. A common sign that eventually can show up is an enlarged thyroid, called a goiter. It can also cause swallowing problems. 

Some other symptoms can include: fatigue, low tolerance to cold, weight gain, heavy menstrual periods, constipation. 

Personally, I've experienced joint pain, fatigue, tingling hands and feet, mild swallowing issues that come and go, cold hands and feet, brain fog, etc.

The Surprising Relief of Having a Diagnosis

 I was actually relieved to hear that my labs were abnormal simply because it validated what I already knew- that there was something wrong and that I wasn't crazy or making things up. It also meant that we now knew more about what was causing the symptoms and how to potentially treat them effectively. 

The Medication Dilemma

I'm generally very leery of medications and have tried to put off trying anything for awhile. My first rheumatologist wanted me to try Plaquenil, which is prescribed as a disease modifier for several autoimmune disorders (she thought I may have seronegative rheumatoid arthritis). I just wasn't ready to try it then and I wasn't comfortable with a diagnosis of exclusion, so I put it off.

My current rheumatologist also asked me to try Plaquenil and did a good job of "selling" it, basically saying is "one of the few drugs that the more we find out about it, the better we feel about it" and that it's pretty gentle. I'd read about one side effect being possible vision issues but he said he's never seen a patient have any vision issues with it. I hope this is true- I'm still a little hesitant but basically I'm just ready to try something (in addition to diet and lifestyle approaches).

In addition to Plaquenil, he also put me on a low dose of Synthroid which is a synthetic compound that is identical to T4 (levothyroxine), a thyroid hormone. It's an extremely low dose to start. 

If my thyroid hormones are normal, why do I need to take thyroid hormones?

This was my main question regarding taking Synthroid. The basic answer I've found (and that my doctor confirmed), is that with Hashimoto's, even if thyroid hormones are normal, taking Synthroid may help to keep you from developing hypothyroidism.

This Clinical Reviews Post talks a little bit about the controversy/debate on whether or not it's a good idea to start hormone treatment when hormone levels are still normal.

I tried to find some more research articles about implications for prescribing Synthroid to patients with normal thyroid hormone function (called euthyroid) but the presence of high thyroid antibodies. I did find plenty, but most of the articles are about fertility, lowering rates of preterm delivery, and promoting a healthy pregnancy. My doctor did mention that there was a chance that my recent miscarriage might have been related to my thyroid issues and that if I wanted to get pregnant again, Synthroid may be helpful. 

Don't give up on your health because you have an autoimmune disorder.

It can be hard to stay positive when you don't feel well and you have something that is considered to be "incurable" and "progressive". It can feel like you're broken or damaged or old or that your good years might be behind you. I've certainly had these feelings over the past year.

In general, it's especially devastating because many people diagnosed with autoimmune disorders are very young and it's only becoming more common.

So what can you do about it? Stay proactive, find a good rheumatologist, connect with others going through the same thing, do your research, and keep working hard to keep your health the best it can possibly be through living a healthy lifestyle.

In regards to working on lifestyle changes, I've read Amy Myers' The Autoimmune Solution and Izabella Wentz' Hashimoto's Protocol Book. Both are incredibly helpful and eye-opening and certainly give me hope that it may be possible to reverse a lot of my symptoms and get well again. Isabella also has a 12 week Hashimoto's self-management program that goes in-depth on things like getting to the bottom of root causes in order to heal, determining which labs you need to ask for and what to do with the results, and being an advocate for your own health. You can register for a free webinar that explains the program by clicking the link below. 

If you feel like something is wrong it probably is. 

What I mean by this is you know your body and you know when you don't feel right.

I started to feel very silly continually calling my doctors, pushing for more answers and asking for more referrals when they said I was completely fine. I felt silly sitting in doctor's office after doctor's office as they looked over my chart and then looked at me seemingly wondering why the heck I was there.

You're not alone if you're going through this. Autoimmune disorders are so tricky and the symptoms can be so vague, that you end up going for a long time without clear answers and maybe taking meds for conditions you don't even have!

If you're going through this, don't give up. Keep pushing forward until you get an answer that fits.

*As usual, the information contained in this post and on this site are my opinions and experiences and are meant to provide useful information. They are not to be construed as medical advice. If you have questions about a health condition, see your doctor. You can read my full disclaimer here

Figuring Out Root Causes

When it comes to figuring out your root causes and triggers, Izabella Wentz (The Thyroid Pharmacist) has a great book and a very extensive program for guiding you through the process.


You can save $100 off the Hashimoto's Self-Management Program by using my affiliate discount link here

The Hashimoto's Self-Management Program is a 12-week self-management, self-paced program for Hashimoto’s patients. It is designed to equip you with strategies that will enable you to start improving faster and have better control of your own health.


I hope you found this post useful. If you have Hashimoto's, how long did it take doctors to figure it out? Leave a comment below!

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