What Causes Hyperthyroidism?

Last Updated on July 20, 2026 by Carrie Korem, FNTP

What causes hyperthyroidism? As someone who has struggled with hyperthyroidism in the past and has also worked with many clients who have hyperthyroidism, I’ve seen first hand what can help. I’ve seen many, many clients with hyperthyroidism go into remission which was confirmed by their doctor. So, let’s dive into the causes of hyperthyroidism so you can better understand what’s going on with your body.

What is hyperthyroidism (over active thyroid)

Hyperthyroidism happens when the thyroid gland makes too much thyroid hormone. This condition is also known as overactive thyroid. Hyperthyroidism speeds up the body’s metabolism.

What Causes Hyperthyroidism?

In the holistic world, we see that the two most common root causes for hyperthyroidism are chronic stress and/or toxicity in the body.

Also, the root cause depends on which level is high or low, so let’s take a look at those:

If TSH is low:

First, let’s clear up something important. TSH is not a thyroid hormone. It’s actually a pituitary hormone. So a low TSH doesn’t automatically mean your thyroid hormones are high.

Here’s how it works. Your pituitary, hypothalamus and adrenals (together they’re called the HPA axis) are all part of your endocrine system. They talk to each other all day long. When your body is under chronic stress, the hypothalamus tells the pituitary to lower TSH. This signals the thyroid to make more hormones so your body can keep up.

So a low TSH doesn’t always point to a thyroid problem. Many times, it’s really an imbalance in the HPA axis. Your practitioner’s job is to dig deeper and find out why that imbalance is there in the first place.

If free T4 is high:

• Most often, free T4 is high because there is a severe form of emotional or environmental stress (from things such as synthetic pesticides, toxic heavy metals, and possibly glyphosate).
• FT4 can also be elevated because TSI is mimicking TSH and telling the thyroid to make excess FT4. This often happens when one has Graves’ disease, so it’s always important to get this level tested.
• There is also a negative feedback loop between TSH and FT4, so sometimes FT4 can be elevated when TSH is too low.
• Free T4 can also be elevated if you happen to be on too much thyroid hormone replacement, so it’s always good a good idea to talk to your doctor or pharmacist about this possibility.
• fT4 can be elevated from overactive thyroid nodules.

If free T3 is high:

Here are a few reasons why FT3 can be too high:

1. The thyroid is making too much T4 that is being converted to FT3.

2. When there is toxicity somewhere in the body, this can increase FT3.

3. Being on too much thyroid hormone can also cause elevated FT3, so it’s always good to talk to your doctor or pharmacist about this possibility.

Don’t ever assume that just because thyroid hormones are high that TSH is low, or that if TSH is low that thyroid hormones are high. Testing is always necessary so you and your practitioner can see the bigger picture.

Here is the list of thyroid labs to ask your practitioner for (or you can order them yourself here):

TSH
fT4
fT3
rT3
TPOab
TgAB
TSI

When to see a doctor

Always work with a doctor when you have hyperthyroidism. The body is in a state of overdrive and it’s incredibly important to be closely monitored.

I’ve worked with many clients who were diagnosed with hyperthyroidism and they were under the care of their doctor while we worked together on their root causes. You can take holistic and conventional steps for your thyroid at the same time!

Can you take holistic steps for Hyperthyroidism while working with a doctor?

Yes! In this article, I list 10 steps you can take to reduce hyperthyroidism symptoms naturally.

Can you reverse Hyperthyroidism naturally?

Yes! I’ve seen it happen for myself, my clients and members of my thyroid course. The key is working on the root causes.

How can I learn more about the steps I can take for Hyperthyroidism?

I have four fantastic options for you!

1. To download my 50 of my top tips to support the thyroid naturally, tap here. I’ll also send you an educational email every few days to help you learn how to support your body naturally.
2. If you’d like to learn from first steps you can take to help support your thyroid, check out my class, “5 Keys to Thyroid Hormone Balance”. It’s just 45 minutes and I promise you’ll learn something new!
3. If you’re looking for a step-by-step plan for Hyperthyroidism that truly works (no more piecing together info!), check out my 90-Day Thyroid Reset Program.
4. Book a consult with me for one-on-one help. Here’s info about what working with me looks like.