Why Thyroid Health Matters for Athletes
- Mar 19
- 5 min read
Updated: 2 days ago
What if your low energy or stubborn performance plateau have little to do with your training and everything to do with your thyroid?
In episode 133 of The Eat for Endurance Podcast, I’m joined by Katie Morra, MS, RD, LDN, IFMCP to break down thyroid health for athletes.
Katie is a Registered Dietitian and Institute for Functional Medicine Certified Practitioner who specializes in complex chronic illness. Through her practice, Gut Honest Truth, she focuses on the identification and treatment of root causes behind chronic inflammatory conditions, autoimmune disease, gastrointestinal dysfunction, and thyroid dysfunction.
In this episode, Katie and I discuss:
What the thyroid actually does and how it impacts almost everything in the body
Common signs of thyroid dysfunction in active people
The connection between underfueling, stress, and thyroid function
Why you should get a full thyroid panel done, and not just test TSH
How gut health impacts nutrient absorption and thyroid function
When someone may need thyroid medication
The difference between Hashimoto’s and hypothyroidism caused by underfueling
Practical nutrition and lifestyle strategies to support the thyroid
This is a complex topic and we only scratch the surface, but it’s a great starting point if you’ve ever wondered whether your thyroid could be playing a role in how you feel or perform.
What You Need to Know About Thyroid Health for Athletes
The thyroid is often misunderstood, both in what it is and what it actually does in our body.
Yes, it’s a small gland in your neck. But as Katie explains, functionally, it acts as the “master regulator of your metabolism,” influencing things like:
Energy levels
Body temperature
Brain function and focus
Heart rate and recovery
Gut function and nutrient absorption
In other words, it touches almost every system in the body.
While many conversations about thyroid health go straight to weight, that is a huge oversimplification for such a complex system. Because when thyroid function is off, the ripple effects can show up in ways that feel very familiar to athletes…which is why it’s so easy to miss.
Common Signs of Thyroid Dysfunction
Many athletes assume symptoms like fatigue or poor recovery are just "part of training." But sometimes, there’s more going on.
Like I tell clients all the time, just because certain symptoms are “common,” doesn’t mean they’re “normal.”
Some potential red flags include:
Persistent fatigue or low energy
Poor recovery or declining performance
Unexplained weight changes
Irregular or missed menstrual cycles
Hair loss or brittle nails
Constipation or other gut issues
Elevated cholesterol despite a solid diet
Fertility challenges
One thing we emphasized in this episode is that these symptoms don’t exist in a vacuum.
A lot of the time, we’re looking at thyroid health in the broader context of:
Underfueling
High training loads
Chronic stress
Gut health issues
Because it’s all connected.
Underfueling, Stress & Thyroid Function
This part of our conversation is where I really want athletes to pay attention, because I see a lot of this in my own practice.
When your body isn’t getting enough energy (or is under another form of stress), it may downregulate thyroid function as a protective mechanism.
Katie described this as your body essentially “slamming on the brakes,” shifting thyroid hormones into a less active form to conserve energy.
I see this all the time in athletes who are:
Training for marathons, ultras, or Ironmans
Underfueling (intentionally or unintentionally)
Trying to do more without enough support
It’s also why simply looking at one lab marker (like TSH) often isn’t enough to tell the full story.
Nutrition, Gut Health & Key Nutrients
We also talked about how nutrition plays an integral role in thyroid health (no surprise there!). Nutrition is always a huge piece of the puzzle.
Some of the most important nutrients for thyroid function include:
Iron
Vitamin D
Zinc
Selenium
B vitamins (especially B12)
Omega-3s
And here’s the kicker: you can be eating “well” and still have issues if your gut isn’t absorbing nutrients properly.
So when we’re looking at thyroid health, we can’t just look at intake, we also have to look at digestion and absorption.
Key Takeaways on Thyroid Health for Athletes
The thyroid impacts nearly every system in your body, not just weight
Fatigue, poor recovery, and performance struggles can be signs of thyroid dysfunction
Underfueling and high training stress can suppress thyroid function
A “normal” TSH doesn’t always mean optimal thyroid health
Nutrient deficiencies (iron, vitamin D, zinc, etc) can impair thyroid function
Gut health plays a critical role in nutrient absorption and thyroid health
Hashimoto’s and underfueling-related thyroid issues are different and require different approaches
There’s no one-size-fits-all solution, so testing and context matter
Want Help Supporting Your Thyroid and Your Performance?
If this episode has you thinking, “okay…this might be me,” I’m here to help.
A lot of athletes I work with come in feeling tired, frustrated, and confused because something feels off, but they can’t quite figure out why.
This is exactly the kind of nuance I help athletes navigate every day. Whether it’s underfueling, GI issues, thyroid concerns, or just wanting to feel stronger and more consistent in your training, you don’t have to piece it together on your own. I offer a variety of nutrition support options so you can choose what works best for you.
Here’s what one client had to say about working together:
"Claire was also incredibly persistent in helping me solve a complicated GI situation—I received many emails that started with “oh, and I had one more idea to try…!”—tapping into her deep knowledge of sports and general nutrition and always seeking new information and suggesting new potential solutions. With her help, I have come so far in dialing in both my sports and daily nutrition, kept GI issues under control, and taken my marathon time down 36 minutes in one year, achieving my first Boston- and New York City-qualifying times. I can’t recommend working with Claire enough, and I truly believe it is what has made all the difference in my active lifestyle. Her advice is truly individualized and realistic—something you can’t get from a few slides on Instagram or a generalized guideline." -Kristina
Here are a few ways to get nutrition support:
Join my low-cost, low-commitment Fuel for Life Crew membership for just $39/month, (cancel anytime)
Browse my nutrition masterclasses (all are also included in the membership)
Grab my Eat for Endurance Mini Guide Bundle (a collection of 6 mini guides, worksheets, and a bonus supplement resource)
Download my free fueling resources
Fill out a new client inquiry form for comprehensive 1:1 coaching (limited spots available)
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Disclaimer: All information provided is for educational and entertainment purposes only and is in no way meant to replace individual medical and nutrition recommendations.
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