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How Hot and Cold Weather Affects Your Thyroid

Knowing how hot and cold weather can affect your thyroid function is essential when you’re hypothyroid.
How Hot and Cold Weather Affects Your Thyroid
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During periods of extreme cold or heat, the thyroid undergoes complex changes to help our bodies adapt to the challenge. These changes are essential for maintaining balance but can also stress the thyroid gland, potentially leading to thyroid-related problems. In this article, we’ll look at the effects of cold and hot weather on people with hypothyroidism and several conditions – including seasonal affective disorder and Raynaud’s syndrome – that can be related to time of year and weather. 

Cold-induced thermogenesis

To understand how cold weather affects your thyroid function, you first need to understand a process called CIT – cold-induced thermogenesis. CIT is the process of generating heat by increasing metabolism in response to cold ambient temperatures to maintain a stable core body temperature. CIT has been measured in humans for centuries but has found renewed interest because of the recent ‘rediscovery’ of thermogenic, cold-activated brown adipose tissue (BAT) in adults. Brown fat activation mediates CIT in adult humans in response to a mild decrease in temperature. CIT can vary depending on factors such as body mass and basal metabolic rate. 

It’s important to understand that hypothyroidism can significantly affect CIT. Thyroid hormones are essential to the proper function of brown adipose tissue BAT and the CIT process. Data from experiments indicate that severe hypothyroidism is associated with drastically reduced CIT. 

Several studies have established the relationship between hypothyroidism and CIT. 

A study published in the journal Thyroid found that even moderate levels of hypothyroidism reduce cold-induced thermogenesis (CIT) in humans. The study also found that sufficient thyroid hormone replacement restores CIT. This suggests that people with hypothyroidism may be more sensitive to cold temperatures and may require adjustments to treatment or lifestyle to feel their best in cold weather.

Another study found that free thyroxine (Free T4) levels are associated with CIT in healthy people with normal thyroid function. Thyroid hormone is crucial for the adaptation to cold.

The good news? A study on patients with subclinical or overt hypothyroidism found that hypothyroidism reduces CIT, and thyroid hormone replacement therapy can restore CIT! 

What can hypothyroid patients expect during cold weather?

Now that we’ve established the relationship between CIT and hypothyroidism, let’s look at how cold weather can affect hypothyroid patients. 

Extreme cold causes your body to conserve heat by reducing blood circulation to your extremities. This can lead to a drop in body temperature and trigger the production of thyroid hormones to compensate for the cold environment. While this response is necessary for survival, it can strain the thyroid and potentially result in imbalances or exacerbate existing thyroid disorders. Specifically: 

Your thyroid can work less efficiently: Cold weather can make the thyroid work less efficiently, which may require thyroid hormone replacement dosage increases and adjustments.

Your T3 and T4 may drop, and your TSH may increase: You may experience a drop in your T3 and T4 levels, along with a corresponding rise in your TSH levels, during colder weather. Your thyroid may be unable to keep up with your body’s hormonal demands. 

You may become cold intolerant: When you’re hypothyroid, you may be cold intolerant because you don’t produce enough thyroid hormone to convert and utilize stored energy effectively. When it’s cold, you’ll have less energy available to regulate body temperature compared to people with normal thyroid hormone levels. When you experience cold temperatures, your body mounts a defense mechanism to preserve heat by drawing blood away from the hands and feet. 

You’re at increased risk of hypothermia: Hypothyroidism slows down metabolism, making people more sensitive to cold temperatures. People with hypothyroidism are also at greater risk of suffering from hypothermia, a potentially life-threatening condition when exposed to cold temperatures.

Your fat metabolism can slow: Fat metabolism can slow down when your T3 levels drop. This can cause an increase in low-density lipoprotein (LDL) – also known as the bad cholesterol – during cold weather.

You may gain weight: A slower metabolism, less exercise, and increased appetite and carbohydrate cravings in cold weather can combine to cause weight gain. 

What can hypothyroid patients expect during hot weather?

In hot weather conditions, our bodies rely on sweating to cool down and maintain a stable body temperature. This process works hand in hand with the thyroid gland, which regulates the body’s metabolism and temperature. However, excessive sweating can lead to dehydration and electrolyte imbalances, affecting the optimal function of the thyroid. It can also exacerbate the symptoms of individuals with pre-existing thyroid conditions, such as hypothyroidism. Here is what you can expect during hot weather: 

Your TSH level may drop: Interestingly, hot weather may slightly improve your thyroid function. One study found that people with subclinical hypothyroidism were nearly 1.5 times more likely to revert to normal TSH levels during warmer weather. 

Heat intolerance: Heat intolerance is more often a symptom of hyperthyroidism. But hypothyroidism – especially when due to autoimmune Hashimoto’s thyroiditis – can cause you to experience poor temperature regulation and make you feel especially overheated during sweltering weather. You may also experience hot flashes due to a spike in thyroid hormone levels.

Your cortisol levels may increase: During extremely hot weather, your stress hormone cortisol may also rise. Hashimoto’s patients frequently have high cortisol levels. Cortisol can counter inflammation in the short term, but a long-term rise in cortisol can cause your immune system to become resistant to the hormone. This can cause an increase in your immune response and flare-ups.

You may lose weight: Your appetite might be suppressed during warmer months. An improvement in thyroid function, the tendency to eat less fatty foods in warmer months, and more time spent outdoors exercising can combine to result in some weight loss. 

The vitamin D connection

Vitamin D levels are linked to hypothyroidism. Specifically, vitamin D deficiency is more common in people with hypothyroidism compared to those with normal thyroid function. Experts believe that vitamin D deficiency may even be a risk factor for hypothyroidism. Interestingly, vitamin D supplementation may improve thyroid function in hypothyroid patients. One randomized, double-blind, placebo-controlled trial found that vitamin D supplementation among hypothyroid patients for 12 weeks improved serum thyroid-stimulating hormone (TSH) levels. Another study found that vitamin D supplementation improved thyroid function in patients with autoimmune Hashimoto’s thyroiditis. 

What does vitamin D have to do with weather? Sunlight exposure!  Sunlight exposure is an essential source of vitamin D. Sunlight exposure also helps regulate the production of melatonin, a hormone that plays a role in sleep-wake cycles and the body’s circadian rhythm. Melatonin production is suppressed by insufficient exposure to sunlight, which can lead to sleep disturbances and other health issues. People with hypothyroidism may already experience sleep disturbances, so getting enough sunlight exposure can help regulate melatonin production and improve sleep quality. Sunlight exposure can also help regulate cortisol production, a hormone that plays a role in stress response and energy levels. Cortisol and thyroid hormone production are closely linked, and high cortisol levels can decrease the body’s ability to convert T4 to T3, the active form of thyroid hormone. Therefore, getting enough sunlight exposure can help regulate cortisol production and potentially improve thyroid function.

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Seasonal affective disorder (SAD) and hypothyroidism

Hypothyroid patients may experience seasonal affective disorder (SAD)  – sometimes called the “Winter Blues.” SAD is a type of depression that occurs during certain seasons, most often in the fall or winter, though some people experience it in summer. The symptoms of SAD are similar to those of depression – and hypothyroidism! – but they become more intense at a particular time of year. Signs and symptoms of SAD may include:

  • Persistent low mood
  • Loss of pleasure or interest in everyday activities
  • Feeling irritable
  • Feelings of despair, guilt, and worthlessness
  • Tearfulness
  • Feeling stressed or anxious
  • Reduced sex drive
  • Becoming less sociable
  • Feeling lethargic (lacking in energy) and sleepy during the day
  • Sleeping for longer than usual and finding it hard to get up in the morning
  • Finding it difficult to concentrate
  • Increased appetite – some people have a particular craving for foods containing lots of carbohydrates and end up gaining weight as a result 

Hypothyroid patients experiencing SAD should first have a complete thyroid panel to determine if they are experiencing seasonal changes in thyroid levels that may explain these symptoms, many of which are similar to those of an underactive thyroid. If your thyroid treatment is optimal, but you still have SAD symptoms, see a healthcare provider to discuss the treatments available for SAD, including light therapy and antidepressants. 

You can also make some lifestyle changes to minimize the symptoms of SAD:

  • Getting outside during the day to get natural sunlight
  • Exercising regularly
  • Eating a healthy diet
  • Practicing stress-reducing techniques, such as meditation or yoga
  • Keeping a regular sleep schedule
  • Spending time with friends and family
  • Taking a vacation to a sunny location

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Raynaud’s syndrome

Raynaud’s syndrome is a condition that causes the blood vessels in the fingers and toes to narrow, which can cause pain, numbness, and tingling, especially when exposed to cold temperatures. There is a relationship between Raynaud’s syndrome and hypothyroidism, and the link may lie in the hormonal imbalances caused by hypothyroidism, as thyroid hormones directly impact blood vessels. Research has found that Raynaud’s occurs in hypothyroidism, and its symptoms disappear with thyroid replacement therapy. 

A typical episode of Raynaud’s lasts about 15 minutes, but attacks may be shorter or longer. The symptoms include:

  • Cold fingers or toes
  • Areas of skin that turn white, then blue, then red when the hands are warmed
  • A numb, tingly, prickly feeling or stinging pain upon warming 
  • Hands that may become swollen and painful when warmed 

If you experience these symptoms during cold weather, talk with your doctor about lifestyle changes, medications, and other treatments to resolve the condition. 

Tips for hypothyroid patients for coping with cold weather

When you’re hypothyroid, you may experience cold intolerance because you’re not producing enough thyroid hormone to convert and utilize stored energy effectively. This can lead to less energy being available to regulate your body temperature, making you more sensitive to cold temperatures. Here are some tips to help you cope better with the effects of cold weather:

Test your thyroid function regularly: If you are always colder than everyone else or you find yourself bundled up when the outside temperature does not warrant winter gear, it may be valuable to test your thyroid function and see if you need a seasonal dosage adjustment. 

Adjust your thyroid medication: Some people who live in seasonal environments with colder winters may need to adjust their thyroid medication to counteract the chill outside. Discuss any changes to thyroid medication with your doctor.

Layer up: Wear warm clothing such as a down jacket, hat, gloves, and scarf to keep your body warm.

Turn up the thermostat: Turn up the thermostat at night to prevent cold intolerance from waking you up. Keep your home temperature warm during the day as well.

Get plenty of rest: Understand that you may need more rest during the colder months, and listen to your body. As the days get shorter and nights get longer, our bodies naturally want to rest more.

Exercise: Exercise can help keep your thyroid-related weight gain in check and improve your mood and sleep. When the weather is reasonably mild, get outside and exercise.

It is important to note that you should seek medical attention immediately if you are experiencing severe cold intolerance or hypothermia.

Tips for hypothyroid patients for coping with hot weather

Hypothyroid patients may experience heat intolerance because they do not produce enough thyroid hormone to regulate body temperature effectively. Here are some tips to help hypothyroid patients cope better with the effects of hot weather:

Test your thyroid function: If you are always warmer than everyone else or sweating excessively, it may be valuable to test your thyroid function. If your levels are even slightly irregular, you are at higher risk of heat intolerance.

Adjust your thyroid medication: Some people who live in seasonal environments with hotter summers may need to lower their thyroid medication dose to counteract the heat outside. 

Stay hydrated: Drink plenty of water to stay hydrated and cool down your body.

Wear light clothing: Wear light-colored, loose-fitting clothing made of breathable fabrics such as cotton or linen to help your body stay cool.

Stay indoors during the hottest part of the day: Avoid being outside during the hottest part of the day, typically between 10 a.m. and 4 p.m. If you must be outside, stay in the shade or wear a hat to protect your head from the sun.

Use air conditioning: Use air conditioning to keep your home or office cool. If you do not have air conditioning, use fans to circulate air and create a breeze.

Exercise in the morning or evening: Exercise during the cooler parts of the day, such as early morning or late evening, to avoid overheating.

It is important to note that you should seek medical attention immediately if you are experiencing severe heat intolerance or heat stroke.

A note from Paloma

Staying on top of your thyroid levels is an important way to navigate cold and hot temperatures. The Paloma Health blood test kit allows you to conveniently monitor your thyroid levels from the comfort of your own home. No more waiting rooms or costly doctor visits. With this kit, you can take control of your health in a simple and hassle-free way.

Also, regular check-ins with your thyroid care provider are essential, as you may need seasonal dosage adjustments. Discover the convenience of a Paloma membership and regularly schedule convenient virtual visits with Paloma Health’s knowledgeable thyroid care practitioners, designed specifically for people with hypothyroidism. With Paloma’s expert medical team, you can ensure optimal treatment for your condition -- no matter the season.

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Vedrana Högqvist Tabor, Ph.D., contributed to this article.


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Mary Shomon

Patient Advocate

Mary Shomon is an internationally-recognized writer, award-winning patient advocate, health coach, and activist, and the New York Times bestselling author of 15 books on health and wellness, including the Thyroid Diet Revolution and Living Well With Hypothyroidism. On social media, Mary empowers and informs a community of more than a quarter million patients who have thyroid and hormonal health challenges.

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