Normal TSH Levels: Your Functional Medicine Guide

Let’s talk about TSH levels, and thyroid labs in general.

We have reliable tests, widely and conventionally available, to measure thyroid function and thyroid hormone levels. So why is there still so much confusion and disagreement around thyroid labs?

In holistic and functional medicine, we see a big problem in the way conventional medicine interprets thyroid tests. Too many patients with thyroid problems are being missed or dismissed, and not getting the care they need– or having to wait around until things get worse.

I’m going to break all of this down today. What is a normal range for TSH levels, what does “normal” even mean in the context of our sickcare system, and what do the numbers on your thyroid labs signal?

Let’s get into it.

What Is TSH?

Thyroid Stimulating Hormone (TSH) is usually the first (or one of the first) labs providers will run when they suspect a thyroid condition. This hormone is released from the pituitary gland and acts as a messenger, signaling your thyroid to produce and release thyroid hormones (T3 and T4).

Basically, TSH works to regulate thyroid function through a feedback loop. When your thyroid hormone levels are low, TSH levels rise, telling the thyroid to produce more.

Healthcare providers rely heavily on TSH to identify thyroid disorders.

If TSH is high, this suggests an underactive thyroid (hypothyroidism). The thyroid isn’t producing enough thyroid hormones, so the pituitary gland is producing more and more TSH to encourage the thyroid to take action.

If TSH is low, this suggests an overactive thyroid (hyperthyroidism). The thyroid is producing too much thyroid hormone, so TSH production is slowing down.

To confirm hypothyroidism or hyperthyroidism, TSH levels are analyzed alongside levels of the thyroid hormone T4 (thyroxine), and sometimes the active form, T3 (triiodothyronine).

What Are Normal TSH Levels?

So, what should your TSH levels be? It depends on who you ask. In conventional medicine, the normal range is generally considered to be between 0.4 and 4.0, or sometimes up to 5.0, mIU/L. (Low TSH levels relative to the range are suggestive of hyperthyroidism; high TSH levels relative to the range are suggestive of hypothyroidism).

In functional medicine, the range we consider optimal is narrower: between 1.8 - 2.5 mIU/L.

Why the discrepancy? It really comes down to what “normal” actually means.

Here’s something I wish more people knew. Reference ranges are usually determined based on a bell curve– a statistical average of everyone being tested at that lab.

The problem is that most of the time, people getting tests done at a lab are experiencing health issues. So when your doctor tells you that your TSH levels are in the “normal” range, what they’re really saying is that your levels are within the average of a population that’s already skewed towards dysfunction. So “normal” is really not the same as “healthy” or “optimal”.

That’s why in functional medicine we use a narrower reference range, based on what we see in patients who are actually thriving. It’s not about perfectionism, but about catching imbalances earlier and getting ahead of more serious problems.

LISTEN: Dr. Amy Myers: Can You Reverse Thyroid Problems? Labs, Food, Supplement + Lifestyle Hacks For Vibrant Hormone Health 

Conventional vs Functional Medicine Thyroid Panels

A standard thyroid test in conventional medicine will include TSH, maybe T4 levels, and maybe T3 levels. But that’s only part of the picture, as I’ll break down here. A functional medicine approach usually involves a more comprehensive panel, looking at multiple thyroid markers that each tell us something different about how your thyroid is functioning.

Why don’t we just look at TSH? TSH is an essential data point and a useful place to start, but it doesn’t always tell the full story. (1)

The problem is that TSH is part of a feedback system involving several different components. If you have issues with hormone conversion, for example, your TSH test results might look normal even though there’s still an underlying dysfunction.

Often when patients have symptoms of hypothyroidism or other thyroid problems but normal TSH levels, they’re told that nothing is wrong. In functional medicine, we recognize that symptoms mean there is something wrong! That’s why we look deeper, running additional thyroid function tests to get a more complete picture of the rest of your thyroid (and overall) story.

Tests we might run beyond TSH include:

• Total T4
• T3 uptake
• Total T3
• Free T4
• Free T3
• Reverse T3
• TPO antibodies (thyroid antibodies)
• Thyroglobulin Ab

These tests help us figure out not just whether your thyroid is overactive or underactive, but also how well your body is converting hormones, whether thyroid autoimmunity is involved (autoimmunity is the most common cause of thyroid disease), and whether stress or inflammation may be interfering with your thyroid function.

To be clear, these aren’t alternative tests. They’re actually conventional blood tests that your provider could easily run, but they generally choose not to, focusing instead on just one or two markers (like TSH).

You can learn more about these different tests, along with conventional and optimal ranges, in my article here.

Why Are My TSH Levels High Or Low?

If your TSH levels are outside of the optimal range, the next step is to figure out why and what’s going on.

I can just hear your conventional doctor saying “it’s because your thyroid isn’t producing enough/is producing too many hormones”. True. But why? The thyroid doesn’t just spontaneously decide to rebel. In functional medicine, we’re always looking for the root cause of dysfunction.

Around 90% of hypothyroidism cases are caused by the autoimmune condition Hashimoto’s (the immune system attacks the thyroid gland). (2) Even then, we need to keep digging. What is underlying this immune system dysfunction?

Here are a few possible root causes of dysfunction: 

• Autoimmune disease (which may be triggered by gut issues, toxin exposure, chronic infections, or unresolved trauma)
• Poor T4-to-T3 conversion (which may be triggered by chronic stress, nutrient deficiencies, or liver or gut dysfunction)
• Thyroid resistance (Receptor sites aren’t responding properly to hormone signals) (3)
• Pituitary dysfunction (in this case, TSH may be low despite low thyroid hormone output)

Contributing factors to these issues may include: 

• Chronic stress; elevated cortisol levels (4)
• Nutrient deficiencies, including in selenium, iron, and/or vitamin D (5, 6)
• Toxin exposure (PFAS and other endocrine disruptors can impair thyroid hormone production) (7)
• Hormonal imbalances
• Gut dysbiosis and/or leaky gut (70% of the immune system lives in the gut, and poor gut health can trigger autoimmunity) (8)
• Liver congestion (the liver plays a key role in hormone conversion)

Identifying these patterns and root causes helps us understand not just that the thyroid is struggling, and not just why the thyroid is struggling, but also what steps we need to take to move forward and heal.

Functional vs Conventional Medicine Treatment Options

In conventional medicine, treatment of primary hypothyroidism or hyperthyroidism typically begins and ends with thyroid medication.

For hypothyroidism, the prescription is usually levothyroxine (Synthroid), a synthetic T4 thyroid hormone replacement. In some cases, liothyronine (T3) or desiccated thyroid (like Armor) may be added. For hyperthyroidism, antithyroid medications like methimazole (Tapazole) are typically prescribed, and in some cases more invasive treatments like radioactive iodine treatment or surgery are recommended.

Those with subclinical hypothyroidism or whose levels of TSH and other hormones are suboptimal but not enough for a diagnosis are basically sent on their way.

In functional medicine, we recognize that:

• Subclinical issues should be addressed before they get worse (we don’t need to wait for a more official diagnosis), and;
• Medication alone isn’t going to fix an autoimmune disease, a conversion problem, or a gut imbalance

Medication is sometimes necessary at least in the short-term, but our goal is to reduce dependency on pharmaceuticals by treating the root cause of dysfunction. We may run additional tests to help zero in on imbalances that need to be addressed, and then treat those imbalances with a combination of specialized dietary approaches, targeted supplements, and lifestyle changes (alongside medication as needed).

READ NEXT: Can Hypothyroidism Be Reversed? 

Beyond Normal TSH Levels

If you’ve been told your TSH levels or thyroid levels are “normal” but you still don’t feel well, or if your TSH normals are off but you don’t know what to do next, my most important piece of advice is to trust your instincts. If you don’t feel well, keep investigating. A normal TSH result doesn’t rule out thyroid dysfunction.

With the right tests, a more comprehensive approach, and a provider who treats you as a whole, not just your labs, healing is well within reach.

For a personalized, root-cause focused, functional medicine approach to your thyroid health, consider booking a consultation with my telehealth team. We’d love to work with you.

As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations for people around the globe.