Stress and the Thyroid: A Conversation with Thyroid Nutritionist Lindsay O’Reilly
Written by Melissa Schenkman, MPH, MSJ
Registered dietitian Lindsay O'Reilly specializes in thyroid disorders and functional nu trition, bringing both professional expertise and personal experience to her work. In this discussion, she shares insights about the critical relationship between stress and thyroid health.
Can you tell us about your background and how you came to specialize in thyroid health?
“I've been a dietician for 19 years, but my focus on thyroid health began about six years ago after I was diagnosed with hypothyroidism during a routine primary care visit. The doctor simply told me I had a thyroid issue, gave me medication, and scheduled a follow-up - with no additional information or guidance.
This experience led me to research and dig deeper into thyroid health, eventually leading me into functional medicine. I discovered this was a huge problem, with many women being dismissed, misdiagnosed, or not given adequate information. It became my passion to work with women with thyroid disorders and educate about thyroid health.”
Can you give us a basic overview of how the thyroid works?
“The thyroid is a butterfly-shaped gland at the base of the neck that works together with the brain - specifically the hypothalamus and pituitary gland - in what we call the HPT axis. This system controls the production and secretion of thyroid hormones. When thyroid hormone levels are low (hypothyroidism), the brain triggers more production. Conversely, when levels are too high (hyperthyroidism), the brain reduces production.
There's a thyroid hormone receptor on every cell in our body, which is why thyroid function affects so many aspects of health. It regulates metabolic rate, temperature control, digestion, gut motility, brain function, and gallbladder health. This wide-ranging influence is why thyroid issues can cause symptoms throughout the body.”
How does chronic stress impact thyroid health?
“The thyroid thrives when the body feels safe. When there are signals indicating the body isn't safe, the thyroid tends to slow down function and metabolism to conserve resources for dealing with stressors. Since the brain controls both the stress response system and thyroid function, it will always prioritize the stress response first. This means that when you're dealing with chronic stress, thyroid regulation takes a back seat.”
What about dietary stress - how can things like restrictive dieting affect thyroid function?
“Under-eating, skipping meals, and restrictive dieting are additional stressors on the body. When you're under-eating, the body interprets this as a danger signal - similar to famine conditions - and slows down processes to conserve resources. This is particularly relevant with practices like intermittent fasting, which, while therapeutic for some, can be problematic for others, especially women who are still menstruating.
I've seen cases where dramatic dietary changes have actually triggered thyroid disorders. This includes clients with histories of yo-yo dieting, anorexia, and even body competition preparation where extreme restriction was involved.”
What are some other stressors that people might not realize affect thyroid health?
“There are many different types of stress that can impact thyroid function:
Situational stress: Work, financial issues, relationships, death of a loved one, divorce
Physical stress: Over-exercising (especially common in women)
Internal stressors: Gut dysbiosis, infections, Lyme disease, toxin exposure, blood sugar imbalances
Environmental stress: Temperature extremes (like excessive sauna use or cold plunging)
None of these things are inherently bad, but their impact depends on duration, your body's ability to recover, and your individual response to the stress.”
What do you recommend for addressing stress to optimize thyroid health?
“First, take an inventory of where stress is coming from in your life - is it work, family, food, exercise? Focus on creating an environment that tells your body it's safe. Some specific recommendations include:
Ensure you're eating three meals a day
Schedule dedicated meal times (like putting lunch on your calendar)
Eat to balance blood sugar with balanced meals
Source good quality foods
Engage in activities that bring you joy
Set boundaries at work and home
Learn to say "no" when needed
For women especially, we tend to put others' needs before our own. When dealing with thyroid issues, it's crucial to prioritize your own needs.”
Why is optimizing thyroid health so challenging?
“Thyroid health is tricky because everyone presents differently. Lab results vary between individuals, and root causes can differ significantly from person to person. Stress plays a major role, particularly in autoimmune thyroid conditions, where stress is often a triggering factor.
The challenge is that while people often want to focus on diet and exercise - things that feel more manageable - addressing stress is crucial but much harder to tackle. It's also harder to see immediate benefits from stress management. When you're doing daily deep breathing exercises, you won't necessarily see your labs improve the next day. But consistency in stress management helps tell your body that things are okay, and over time, this helps develop a more appropriate stress response instead of staying in fight-or-flight mode.”
How does sleep affect thyroid function?
“Poor sleep or insufficient sleep can be another significant stressor on the thyroid. Sleep issues can manifest as trouble falling asleep or waking up in the middle of the night. Lack of sleep also impacts blood sugar levels and can worsen insulin resistance, which creates additional stress on the body.
If you're not sleeping well, those 5 AM workouts might not be the best choice. It's important to prioritize sleep and potentially rearrange your schedule to ensure you're getting adequate rest. This might mean exercising at a different time of day.”
What's your guidance on exercise for people with thyroid issues?
“Exercise needs to be individualized based on your thyroid health and stress levels. If you've been extremely stressed for a long time and have low cortisol, intense exercise might not be beneficial and could make you feel worse. However, if you have decent energy and feel good during and after exercise, walking is excellent - whether it's 15 minutes, 30 minutes, or an hour. Walking tends to be lower intensity and doesn't raise stress hormones as much as high-intensity exercises like HIIT classes or extended running.
I also recommend weight lifting, which can be great for many reasons and can be done at low intensity. The key is proper recovery after exercise - doing some deep breathing, mobility work, or yoga to help your body return to a parasympathetic state.
The main takeaway is to make sure your body feels safe. Nourish your body, take care of it, and if you're struggling with thyroid issues, don't hesitate to get help in identifying your triggers and stressors. Even if you just suspect thyroid issues, consider how stress might be impacting how you feel.”
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