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Who Needs Thyroid Hormone Replacement Therapy?

Written by Dr. Michael Ruscio, DC on November 15, 2024

Written by Dr. Michael Ruscio, DC on November 15, 2024 — Reviewed by Kellie Blake

• A Quick Guide to Thyroid Hormones|
• Do You Need Thyroid Medication?|
• T3 Versus T4|
• Your Gut Could Be Behind Your Thyroid Symptoms|
• Diet|
• Probiotics|
• Thyroid Nutrients|

When you have an underactive thyroid, you can easily be overwhelmed by all the information out there on how to treat it.

To be honest, neither functional nor conventional medicine has done a great job when it comes to thyroid problems and how to deal with them. Though there are some examples of excellent patient-centered treatments for hypothyroidism and subclinical hypothyroidism, there’s too much dogmatic opinion about what exactly is the “right” or “wrong” treatment.

In this article, I’ll take an unbiased look at thyroid hormone therapy for people with hypothyroid symptoms. While medication tends to be overused and isn’t the first choice for everybody, it should still be on your radar. 

For instance, there are clear circumstances where thyroid hormone replacement therapy is the right choice — for example, when your thyroid hormone levels are outside normal limits.

Moving forward, you can use this article to identify who needs thyroid hormone replacement therapy and who doesn’t.

I’ll also spell out the  improvements to your gut health that can help bring your thyroid gland back into balance.

First, let’s look at the hormones involved in healthy thyroid function and what can go wrong when they get disrupted. 

A Quick Guide to Thyroid Hormones

The thyroid gland produces two main thyroid hormones that play a crucial role in keeping your metabolism running. These hormones are 1:

• Tetraiodothyronine, also called thyroxine or T4 (the synthetic form of T4 used in medication is known as levothyroxine)
• Triiodothyronine, also known as T3 (this is the more active form of the two hormones)

T4 is produced in higher quantities than T3, but the body can convert T4 into T3 when needed. Together, T4 and T3 increase your metabolic rate, making all of your cells more productive. The effect, in adults, is to:

• Increase your pulse and make your heart beat stronger
• Burn fuel (calories) more quickly 
• Activate the nervous system to ensure better concentration and faster reflexes

To fine-tune your levels of thyroid hormones, the thyroid gland needs help from the pituitary gland, which produces thyroid stimulating hormone, or TSH. 

When your T3 and T4 levels drop, TSH tells your thyroid gland to release more of each hormone. As your T3 and T4 levels get higher, your pituitary gland shuts off TSH until your levels of T3 and T4 begin to fall again. This feedback loop constantly cycles to keep your thyroid hormones in check. However, the cycle can sometimes go awry, resulting in too little thyroid hormone production, which causes your metabolic rate to fall.

In people who get enough dietary iodine, the most common reason the TSH-thyroid hormone feedback loop gets disrupted is the autoimmune condition Hashimoto’s thyroiditis. In Hashimoto’s, the body’s own immune system attacks and damages the thyroid gland and its ability to produce T3 and T4. The typical sign of Hashimoto’s is an elevated level of thyroid peroxidase antibodies 2.

While Hashimoto’s is a common cause of hypothyroidism, having the autoimmune disease doesn’t mean you will definitely go on to become fully hypothyroid. 

But if you notice common symptoms of hypothyroidism, including fatigue, weight gain, cognitive issues (brain fog), dry skin, hair loss, and feeling cold, your thyroid gland could use some love.

The good news is that if you tackle the underlying autoimmune condition, you may never become fully hypothyroid, and you may never need thyroid hormone treatment. One of the most effective ways to help autoimmune conditions is to improve your gut health, and I’ll devote a section to that later. First, I’d like to help you find out if you need thyroid hormone replacement therapy.

Determining Whether You Need Thyroid Medication

Despite what the internet would have you believe, diagnosing and treating overt hypothyroidism — which means you don’t have enough thyroid hormone — is straightforward. 

For example, it’s pretty clear cut that you’ll need thyroid hormone replacement therapy if your thyroid gland has been removed (thyroidectomy) and can no longer make thyroid hormones.

If that’s NOT your situation, a simple blood test can measure your levels of TSH and free T4 (T4 that is not attached to a protein in the blood). That information will give an accurate picture of whether you have true hypothyroidism and need thyroid hormones.

• The healthy range of TSH is about 0.45−4.5 IU/mL 3. 
• The healthy range of free T4 is 0.82−1.76 ng/dL 4.

If your free T4 is below its normal range and your TSH is above its normal range, this indicates true hypothyroidism. 

You can correct this with thyroid hormone replacement therapy and improve the medication’s effects with healthy lifestyle changes.

In contrast, high TSH with normal free T4 suggests subclinical hypothyroidism. 

You probably do not need thyroid hormones to treat this. You can likely treat it by tackling your gut health and the autoimmune issues that often underlie subclinical hypothyroidism.

Importantly, both true and subclinical hypothyroidism are commonly over-diagnosed  5 6 7 8.

This is especially true in older people because TSH levels naturally rise with age, but many clinics do not take this into account when making a diagnosis 9. In fact, the standard lab ranges don’t apply if you are over 60 years old. (They also don’t apply if you are pregnant.)

Case in point: a 2021 study of over 2,500 older people found that the estimated prevalence of subclinical hypothyroidism dropped hugely (to 10% of the original estimate) when clinicians used an adjusted, age-appropriate TSH reference range instead of the standard range detailed above 10. 

Therefore, if you are over 70 years old, having a TSH of up to 8 IU/mL may NOT require treatment. 

In fact, a good rule of thumb I like to borrow from the accomplished thyroid expert Dr. Antonio Bianco is that for each decade of your older life, you can essentially go up a value of TSH. So,

• If you are in your 60s, it’s okay to have TSH in the 6s. 
• In your 70s, it’s okay to have TSH in the 7s.
• In your 80s, it’s okay to have TSH in the 8s, and so on.

This is highly relevant because chronically over-suppressed TSH, a side effect of unnecessary treatment with thyroid hormone, can lead to worse sleep and higher anxiety levels 11. 

T3 Versus T4: What’s the Best Thyroid Hormone Replacement Therapy?

If your thyroid hormones suggest hypothyroidism, a conventional doctor will likely prescribe T4 hormone (levothyroxine) only. The rationale for using T4 alone is that your body will then go ahead and convert an appropriate amount of T3 from this hormone, as needed.

However, many functional health practitioners use a combination of T4 and T3 as thyroid hormone replacement therapy. The combo approach is based on a theory that T4 has a hard time converting to T3, so a combination of both seems more effective than relying solely on the body to do that conversion.

Many of my hypothyroid patients also believe it’s best to have combined T4 and T3 hormones. They’re often surprised when I steer them toward taking T4 hormone alone. But I do this, at least in the beginning, because, despite the hype, the evidence suggests that joint T4–T3 therapy is not better than standard T4.

At the clinic, we have extensively reviewed the evidence examining the use of combination therapy. One meta-analysis (the highest quality type of research) and 16 randomized clinical trials have shown that there is no reliable evidence that a combination of T4 and T3 is better than standard T4 medication for treating symptoms. 

A review paper also found that in 6 out of 8 studies, combination T4–T3 treatment was not associated with any difference in quality of life, but patients still preferred it over T4 alone 50–70% of the time 12. 

The preference for combining T4 and T3 over T4 alone is hard to explain. Clinically, there seems to be no difference between the two. However, some people may prefer combo therapy because they’ve heard it’s better, which helps them feel better via the placebo effect when taking it. It’s also possible that combo therapy leads to subtle, subjective health improvements that studies haven’t been able to objectively measure 12. 

For two reasons, I prefer to take a pragmatic approach with patients who have overt hypothyroidism. The first reason is the lack of support for combo therapy in high-quality research. The second reason is that excess T3 can have side effects, including increased fatigue, worsened mood and sleep, higher anxiety levels, and more symptoms for those with thyroid cancer 11. I’ve seen patients taking too much T3 who have suffered with these symptoms for years before coming to the clinic.

Therefore, I tend to start hypothyroid patients on T4 medication alone. If T4 monotherapy doesn’t resolve their symptoms, or if they feel unhappy with their results, then I’ll advise them to move on to a combination of T3 and T4.

It’s worth noting that practice guidelines from the European Thyroid Association recommend caution in prescribing combination T4–T3 therapy for the 13 treatment of hypothyroidism 13, and the American Thyroid Association does not recommend combining T4 and T3, 14.

The Real Reason Your T3 May Be Low

Low T3 levels may be a byproduct of poor nutrition, gut inflammation, and chronic illness 15. So, rather than taking a hormone replacement for low T3 levels, you’ll likely be better off treating gut imbalances and nutritional deficiencies.

Your Gut Could Be Behind Your Thyroid Symptoms

To summarize what we have discussed so far, it’s common for doctors to incorrectly prescribe thyroid replacement therapy, and to overdiagnose subclinical hypothyroidism, particularly in older people.

Now, let’s move onto another reason that practitioners may get thyroid treatment wrong: they may actually be shooting at the wrong target. In other words, what appear to be thyroid symptoms may actually be the symptoms of an unhealthy gut. 

To be more specific, depression, brain fog, fatigue, and a general lack of well-being can be symptoms of an underactive thyroid disorder. But these are also symptoms that can stem from suboptimal gastrointestinal health.

At the clinic, we have become used to meeting thyroid patients whose lingering hypothyroid-like symptoms cleared up after they improved their gut health. In fact, we published a case series and literature review to alert other functional and integrative practitioners to this observation.

The Gut-Thyroid Axis 

Not only can gut disorders masquerade as hypothyroidism, but there’s also a clear link between gut health and thyroid disease. The connection starts with the fact that Hashiomoto’s thyroiditis — the precursor to most cases of hypothyroidism in parts of the world that have sufficient dietary iodine — is an autoimmune condition. What does that have to do with the gut? Well, around 70–80% of your immune cells are found within your gut 16 and those are the same immune cells potentially fighting your thyroid gland.

When things go awry in both the gut and thyroid, an unbalanced gut microbiota (dysbiosis) is often the common thread 17. Dysbiosis is known to cause or be connected with 18 19:

• Inflammation, increased intestinal permeability (leaky gut), and altered immune responses (remember: Hashimoto’s thyroiditis is an autoimmune disease)
• Altered activity of enzymes that impact thyroid hormone levels
• Reduced absorption of minerals that are important to the thyroid gland
• Brain fog, depression, and other cognitive issues that are similar to hypothyroid symptoms 

As we’ve found many times in the clinic, when we take care of gut problems, thyroid health also improves, sometimes considerably.

To help with improving thyroid symptoms, I generally suggest a three-part gut-friendly plan — namely, making healthy diet changes, taking probiotic supplements, and if needed, supplementing with specific nutrients that nourish the thyroid gland.

Let’s briefly look at these three steps.

1. Find a Gut Health Diet That Works for You

There’s no single gut health diet that is perfect for everybody. However, the general principles of a gut-healthy diet are that it should: 

• Be anti-inflammatory
• Help keep your blood sugar balanced
• Exclude any foods your gut is sensitive to (which will be personal to you)

Many of my patients do well using a Paleo diet framework, as it checks the above boxes without being overly restrictive.

Pinpointing Food Sensitivities

Research suggests that gluten and lactose may be the two most common sensitivities patients with thyroid autoimmunity experience.

For example, two studies showed lactose restriction and a gluten-free diet were associated with significant decreases in TSH levels for Hashimoto’s patients on thyroid medication 20 21.

Not everyone with thyroid symptoms will need to remove lactose and gluten from their diet. However, it is vital to get on top of any food sensitivities you do have. Foods that inflame and damage the gut lining can keep your intestines from absorbing nutrients and medication, and they can also worsen auto-immunity.

Some people find their thyroid and gut symptoms worsen when they eat too many carbohydrates and prebiotic fibers (like those in onions, asparagus, and garlic). If this is you, and particularly if you have pre-existing irritable bowel syndrome, a low FODMAP diet may be more suited to your needs 22.

As your gut heals, you’ll be able to tolerate more foods and get back to a more varied diet, which is ultimately good for your microbiome. You can find much more detail about elimination diets and how to do them safely for thyroid conditions if you sign up for my Thyroid Self Help Guide.

2. Take Probiotics 

A well-formulated, multi-species probiotic supplement can work alongside a gut-healthy diet to help promote a healthier microbiota and ease gut and thyroid symptoms. Interestingly, one study found that a combination of probiotics and prebiotics reduced the need for the T4 medication levothyroxine 23. 

In the clinic, we’ve developed a multistrain approach we call triple probiotic therapy. It consists of validated probiotic strains from three major probiotic categories:

• Lactobacillus & Bifidobacterium species
• Saccharomyces boulardii (a probiotic fungus)
• Bacillus species (soil-based probiotics)

Through trial and error and patient feedback, we have found this three-pronged approach to produce the best symptom relief for our patients.

So far, we only have anecdotal evidence that using probiotics from all three categories is beneficial for thyroid health. But we do have clinical studies showing that multistrain probiotics are more effective than single-strain versions for improving gut conditions, including IBS and constipation 24 25 26. 

Every thyroid patient is different, and you might get a good benefit from just one or two probiotic strains. But trying the triple combination is definitely worthwhile, especially if you haven’t seen much benefit from probiotics in the past.

3. Add in Thyroid Nutrients

As a final helping hand for an underactive thyroid, it’s a good idea to check that you are getting the micronutrients you need for the general good health of your thyroid gland. Thyroid-friendly nutrients include zinc, iron, selenium, and vitamin D. However, of these, the last two can be particularly hard to get from a balanced diet, meaning supplements may be warranted. 

• One meta-analysis concluded that taking vitamin D supplements may bring down elevated levels of thyroid antibodies, indicating an improvement in thyroid autoimmunity 27.
• A clinical trial of patients with autoimmune hypothyroidism found that those who received 200 micrograms of selenium daily for three months also showed significant improvements in thyroid antibodies 28.

Not all research agrees, but because it is neither expensive nor invasive to take vitamin D and selenium supplements, it’s reasonable to try them and see how your symptoms respond. Just make sure to check your vitamin D levels periodically so they don’t get too high.

Thyroid Hormone Treatment Doesn’t Have to Be Complex

If a lab test indicates you have overt hypothyroidism, standard treatment with T4 thyroid hormone is generally the best option. 

That said, rushing to any sort of thyroid hormone medication isn’t a good idea when you have subclinical hypothyroidism. In that case, your best bet is likely to take care of your underlying gut health. Indeed, rebalancing your gut may help reduce symptoms such as brain fog and fatigue that are typical of both gut problems and hypothyroidism.

If you’d like to work through your thyroid issues in more depth, please reach out for a virtual one-to-one consultation with one of our highly experienced practitioners.

The Ruscio Institute has developed a range of high-quality formulations to help our clients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you. The information on DrRuscio.com is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.