Exhausted And Can’t Lose Weight? It Could Be Hashimoto’s

Why Hashimoto’s Is So Often Missed

In the early stages of Hashimoto’s, people often already have signs and symptoms, but their tests can come back normal, or even show an overactive thyroid. This is because the destruction of thyroid cells happens intermittently, not all at once.¹

On top of that, standard testing usually looks at TSH only, and sometimes free T4. T3, your active thyroid hormone, is not routinely tested, and neither are thyroid antibodies.² So someone can have TSH and T4 within range, T3 on the low side, and raised thyroid antibodies, and still be told everything is fine.

The Symptoms Worth Paying Attention To

None of these confirm a thyroid problem on their own, but together they are worth investigating:³

• Fatigue
• Weight gain, or being unable to lose weight
• Feeling cold, cold hands and feet
• Brain fog and trouble concentrating
• Hair loss, thinning hair and eyebrows
• Dry skin and brittle nails
• Constipation, gas and bloating
• Low mood or depression
• Joint and muscle pain
• Heavy or irregular periods, low libido, fertility problems
• Puffy face and swollen eyelids
• Headaches

What A Full Thyroid Picture Actually Looks Like

When I look at thyroid health, I want to see more than two markers. A comprehensive thyroid panel includes:

• TSH, the signal from your brain asking the thyroid to work
• Free T4, the storage form of thyroid hormone
• Free T3, the active form your cells actually use
• Reverse T3, an inactive form that can block T3 from doing its job
• Thyroid peroxidase (TPO) antibodies and thyroglobulin antibodies, the markers of the autoimmune attack

In naturopathic nutrition, the optimal range for TSH is 2.5 or less,⁴ and ideally I like to see it no higher than 2. Higher TSH levels together with thyroid antibodies increase the risk of an underactive thyroid progressing to full hypothyroidism.⁴

Reverse T3 is the piece most people have never heard of. Your thyroid mainly releases T4, and most of your active T3 comes from converting T4 in other tissues, mainly the liver and kidneys. T4 can be turned into active T3, or into reverse T3, which is inactive.⁵ When reverse T3 goes up, the effect of T3 goes down, and this can look exactly like an underactive thyroid. Reverse T3 increases with high stress, zinc, selenium or iron deficiency, poor liver function, and fasting or strong calorie restriction.

The Gut And Thyroid Connection

This is the part I find most important, and the one that’s almost never discussed in a standard appointment.

An imbalanced gut microbiome negatively affects thyroid function. Gut microbes help regulate how iodine is absorbed and recycled.⁶ ⁷ In autoimmune thyroid disease, it’s common to see low production of short-chain fatty acids (the protective compounds your good bacteria make), raised zonulin, a marker of increased intestinal permeability (“leaky gut”), and raised LPS, a bacterial toxin in the blood that drives chronic low-grade inflammation.⁶ ⁷

Food matters here too:

• Gluten. Hashimoto’s often exists alongside coeliac disease, and a gluten-free diet has been shown to lower thyroid antibodies in women with Hashimoto’s.⁸ Part of the reason may be molecular mimicry: gliadin, a protein in gluten, resembles transglutaminase, an enzyme that is abundant in the thyroid gland.⁹
• Lactose. In Hashimoto’s patients with lactose intolerance, restricting lactose was followed by a decrease in TSH levels.¹⁰

What Can Trigger Or Drive Hashimoto’s

Hashimoto’s rarely has a single cause. The factors I look at include:

• Infections. Epstein-Barr virus and H. pylori are often implicated.¹
• Too much iodine. Highly iodinated thyroglobulin is more likely to trigger an immune reaction.¹¹
• Chronic stress. It slows thyroid hormone signalling, reduces T3, raises reverse T3, and shifts the immune system in a direction that predisposes to autoimmune thyroid disease.¹²
• Heavy metals. Mercury, for example, is linked to raised thyroid antibodies.¹³
• Environmental chemicals. Triclosan, found in some toothpastes and personal care products, has a structure that resembles thyroid hormones.¹⁴ Chlorine from swimming pools is linked to raised TSH and thyroid antibodies, and fluoride interferes with iodine uptake and with the conversion of T4 into T3.¹⁵ ¹⁶
• Poor sleep. Sleep apnoea and Hashimoto’s appear to influence each other.¹⁷
• Genetics. Variations in genes such as VDR (the vitamin D receptor) are linked to autoimmune thyroid disease.¹⁸

Your Thyroid Doesn’t Work In Isolation

Hashimoto’s rarely shows up on its own. Two conditions I always keep in mind are oestrogen dominance and PMOS, formerly known as PCOS.

Oestrogen dominance is a state of excess oestrogen activity, for example too much oestrogen relative to progesterone, or oestrogen that isn’t being properly detoxified and eliminated. It is associated with thyroid dysfunction, including Hashimoto’s, as well as with insulin resistance, fibroids, PMS, brain fog, anxiety and depression.

PMOS (polyendocrine metabolic ovarian syndrome) is the new name for PCOS (polycystic ovary syndrome). It was officially renamed in May 2026 after a global expert consensus, because the old name suggested the condition is caused by ovarian cysts, which it isn’t. The new name describes what it really is: “polyendocrine” for the several hormonal imbalances that interact with each other, “metabolic” for features such as insulin resistance and weight gain, and “ovarian” for its effect on ovulation.¹⁹

PMOS affects 5 to 20% of women of reproductive age, and autoimmunity such as Hashimoto’s is one of its possible complications.²⁰ ²¹ Insulin resistance is the most common driver in the majority of PMOS cases, seen in 75% of lean women and 95% of women with obesity who have PMOS, and it can lead to weight gain, which in turn makes PMOS symptoms worse.²²

Blood sugar imbalance and stress hormone (HPA axis) imbalance are also among the common triggers and drivers of thyroid disorders, which is why reducing inflammation and insulin resistance is part of the naturopathic approach to an underactive thyroid.

That’s why I look at all of these things together. Your thyroid is connected to your gut, your sex hormones, your blood sugar, your stress response and your liver. To understand what is actually causing your hypothyroidism, we need to understand how all your body systems are working, rather than just topping up thyroid hormone and hoping the symptoms go away.

The Nutrients Your Thyroid Depends On

Your thyroid can’t make or activate its hormones without the right raw materials:²³

• Selenium helps convert T4 into T3, and supplementation has been shown to significantly reduce thyroid antibody levels in autoimmune thyroiditis.²⁴ It has a narrow therapeutic range though, so more is not better.²⁵
• Vitamin D deficiency is significantly more common in autoimmune thyroid disease, and vitamin D levels are inversely linked to thyroid antibodies.²⁶ ²⁷ (If you missed it, I wrote a whole article on why “normal” vitamin D often isn’t enough.)
• Iron is needed by thyroid peroxidase, the enzyme that makes thyroid hormone, and iron deficiency lowers T4 and T3 and the conversion of T4 into T3.²³
• Zinc supports the conversion of T4 into T3 and the receptors that respond to thyroid hormone.²⁸

A word of caution on iodine: iodine supplements should not be used in autoimmune thyroid disease, or alongside thyroxine.²⁹ Iodine content in kelp and seaweed supplements also varies hugely.³⁰ Please don’t start an iodine or kelp supplement because you read that it’s “good for the thyroid”.

If You’re On Thyroid Medication

Levothyroxine (synthetic T4) is the first-line conventional treatment.³¹ This isn’t about replacing it. But if you’re taking it and still don’t feel well, it’s worth knowing that medication often doesn’t work as hoped because of conversion problems, such as nutrient deficiencies, which is exactly where nutrition comes in.

Its absorption can also be reduced by things like low stomach acid, acid-reducing medication (PPIs) and coffee.³¹ ³²

Three Things You Can Do This Week

1. Ask for the full picture. If you’ve only ever had TSH and free T4 tested, ask your doctor about free T3, reverse T3, and TPO and thyroglobulin antibodies. If you already have results, look at whether antibodies were ever checked.

2. Reduce your exposure to thyroid disruptors. Drink filtered water, choose a fluoride-free toothpaste, eat organic where you can, avoid processed foods and plastic packaging, limit time in chlorinated pools, and switch to natural cleaning products.¹⁵ ¹⁶

3. Keep eating your greens, just cook them. Raw brassicas like broccoli, kale and cabbage contain goitrogens, which can reduce iodine uptake,³³ but cooking, steaming or boiling deactivates them, and it is still beneficial to include these vegetables.³⁴ ³⁵

What This Doesn’t Cover

You won’t find a protocol or a list of supplements in this article, and that’s on purpose. Hashimoto’s is never just about one missing nutrient, and what helps one woman can be useless, or even in certain cases harmful, for another. The right approach depends on your unique health situation: your full thyroid results and antibodies, your nutrient levels, your gut health, your hormones, your blood sugar, the medications you take, and your health goals. Taking the wrong thing, like iodine, can make things worse.

This is exactly what we look at together in a free clarity call. If you already have blood tests, bring them, I’ll review your existing labs and look at them through a functional lens, to spot patterns that standard ranges can miss. Then we can build a plan that’s specific to your body and compatible with any medication you’re on.

If you’ve been told your thyroid is “normal” but you still don’t feel like yourself, that’s where I come in.

Together, we’ll make sure you get the right testing for your situation, not just your thyroid, and I’ll help you advocate for yourself with your doctor. Then we’ll uncover what’s really driving your metabolism and address the root cause for your long-term health.

So that you can start thriving again, the way nature designed you.

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References

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² National Institute for Health and Care Excellence (2019) Thyroid disease: assessment and management (NICE guideline NG145). London: NICE. Available at: https://www.nice.org.uk/guidance/ng145

³ Chaker, L., Bianco, A.C., Jonklaas, J. and Peeters, R.P. (2017) ‘Hypothyroidism’, The Lancet, 390(10101), pp. 1550-1562.

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⁷ Virili, C., Stramazzo, I. and Centanni, M. (2021) ‘Gut microbiome and thyroid autoimmunity’, Best Practice & Research Clinical Endocrinology & Metabolism. Available at: https://www.sciencedirect.com/science/article/abs/pii/S1521690X21000233

⁸ Krysiak, R., Szkróbka, W. and Okopień, B. (2019) ‘The effect of gluten-free diet on thyroid autoimmunity in drug-naïve women with Hashimoto’s thyroiditis: a pilot study’, Experimental and Clinical Endocrinology & Diabetes, 127(7), pp. 417-422.

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