You've been told your thyroid results are normal. Yet you still wake up tired, feel cold when everyone else is comfortable, and watch the scales creep up no matter what you do. If that sounds familiar, you're not alone, and you're not imagining it.
On a recent episode of the Health Up Podcast, I spoke with Dr Sam Shay, DC, a functional medicine certified practitioner, international trainer for Fitgenes genetics and (as it happens) a professional stand-up comedian. Dr Sam has a talent for turning complicated biology into pictures you can actually remember. Here's what I took away from our conversation about why your thyroid might be the missing link.
Your cells run on tiny energy factories
To understand the thyroid, Dr Sam says, you first need to understand the mitochondria. These are the powerhouses of your cells, and he describes each one as an electricity factory.
Like any factory, it needs many moving parts working together. In his analogy, the walls are made of specialised fatty acids, CoQ10 is the conveyor belt, vitamins are the machines and minerals are the computer chips that run them. Fuel arrives from three "truckers' unions" (fats, proteins and carbohydrates), and each one is paid in different nutrient currencies.
Burning fuel with oxygen creates sparks, which we call free radicals. So the factory also needs janitors to put the sparks out before something catches fire. Dr Sam names three key antioxidant enzymes here: manganese superoxide dismutase (MnSOD, which he affectionately calls "Mr SOD", the head janitor), glutathione peroxidase (GPX1) and catalase.
Why does this matter? Because, as Dr Sam puts it, electricity drives everything. Your cell is like a small city, and a city without reliable power quickly runs into trouble. When something in the factory isn't working, you make less energy, and problems follow.
Where the thyroid comes in
Dr Sam describes the thyroid as sitting upstream of the mitochondria. It sends out the engineers.
The thyroid makes T4, which he pictures as a car with four tyres (the tyres being iodine). It travels along the "arterial superhighway" into your cells. There, it transforms into T3, which becomes the engineer that presses the buttons on the factory's control panel to turn up energy production.
When thyroid function is low, the mitochondria lose a big part of the signal telling them to ramp up. The result, he explains, can be that familiar, heavy, low-energy feeling.
Survival mode puts your thyroid on hold
One of the most useful ideas from this episode is the relationship between the thyroid and the adrenal glands.
Dr Sam describes the thyroid as the organ of long-term healing, growth and repair. The adrenals, on the other hand, are about short-term survival. When you're under chronic stress, whether that stress is physical or something you keep replaying in your mind, short-term survival takes priority. Resources are diverted to surviving rather than thriving, and thyroid function gets turned down.
For many of the busy people I work with, that rings very true. Career, family, caring for parents and a never-ending to-do list can keep the body in survival mode for years.
Why one number may not tell the whole story
Dr Sam's interest in the thyroid started in New Zealand, where he practised for eight years. Within a month of arriving, he saw his first goitre, something he had assumed belonged to the history books.
In 2014, a patient came to see him with almost every classic sign of an underactive thyroid. Her TSH had been tested and reported as normal. Dr Sam found a lab that offered a comprehensive thyroid panel, and the broader results pointed to Hashimoto's. In his words, her TSH was "medically normal" but not "functionally optimal". That experience became his launch pad into functional medicine.
He now thinks about thyroid investigation in three layers:
- Testing TSH alone.
- Testing all of the thyroid markers.
- Looking at the other hormones, biochemistry and physiology that may have pushed the thyroid off course in the first place.
Six things that influence your thyroid
That third layer is where Dr Sam spends most of his time. He outlines six areas to consider.
1. Genetics. Your genes can show whether you lean towards higher inflammation, how quickly your "janitor" enzymes work, how you detoxify, how you respond to caffeine or histamine, and even which foundational eating style may suit you best. Dr Sam sees genetic testing as the highest-value test because the information stays relevant for life.
2. The mitochondria themselves. Dr Sam has seen people with optimal thyroid results who still have the signs of low thyroid. The engineer is fine; it's the factory that's struggling.
3. The adrenals. As above, ongoing stress shifts the body into survival mode and the thyroid steps back.
4. Oestrogen. Dr Sam explains that too much oestrogen can slow the thyroid, which is one reason he believes women are more often affected.
5. Nutrients and heavy metals. Making healthy thyroid hormone needs nutrients such as iron, selenium, iodine, tyrosine, B vitamins, vitamin D and vitamin A. He notes that heavy metals like mercury can interfere, including by tying up selenium.
6. The gut. If you're not digesting and absorbing well, you won't get the nutrients you need. Dr Sam also discusses intestinal permeability (often called leaky gut) and how certain infections and gluten have been studied in relation to the immune response against the thyroid.
Testing to save time and money
Dr Sam acknowledged that a long list of tests can feel overwhelming. His view is that testing actually saves time and money, because it shows you what to prioritise. Rather than guessing or chasing the latest supplement, you know what to focus on and when to stop.
If you suspect a thyroid issue, these are the three tests he would start with:
- A comprehensive thyroid panel, including at least TSH, free T3, free T4, reverse T3, anti-TPO and anti-TG antibodies.
- A genetics test, because the results are useful for your thyroid and for every other area of health, for life.
- A gut test, to look at digestion, absorption, hidden infections and intestinal permeability.
My reflections
What I love about Dr Sam's approach is that it's holistic. He doesn't stop at one result. He steps back, looks at how hormones, gut health, nutrients, stress and genetics connect, and then explains it in a way people can picture.
That understanding is empowering. When you can see what's happening inside your body, you move into the driver's seat.
If you've been told your thyroid is fine but you don't feel fine, consider taking these questions to a practitioner who will look at the bigger picture.
Listen to the full episode
You can hear my full conversation with Dr Sam Shay on the Health Up Podcast. To learn more about his work, visit drsamshay.com or fitgenesusa.com, where you'll also find his podcast. In Australia, you can find a Fitgenes practitioner at fitgenes.com.au, and in New Zealand at nutrascript.co.nz.
This article is general information only and is not medical advice. Please speak with your own health practitioner about your individual situation.