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As well as cold intolerance, where you can be extremely sensitive to cold temperatures, heat intolerance can be a symptom of thyroid disease, too. This symptom can also be made worse by rising temperatures outside.
If you feel easily hot, especially compared to others around you, have hot flushes and don’t do particularly well in warm weather, this may suggest that you experience heat intolerance. This can be linked to hypothyroidism for a few reasons.
Over Medication for Hypothyroidism
I would firstly check that you’re not over medicated on your thyroid medication, as being so can lead to hyperthyroidism and thus cause symptoms such as feeling hot, flushed and anxious (see here for hyperthyroidism heat intolerance).
You need a full thyroid panel (note: full, not just one or two tests) doing to include TSH, Free T3, Free T4 and Reverse T3 and thyroid antibodies TPOab and TGab wherever possible. A suppressed TSH can be normal on thyroid meds containing T3, but your Free T3 and Free T4 should be within range, for hyperthyroidism to not be present. TSH alone is not accurate to go by. Please see optimal levels here. 
Another thing to keep in mind is that if you have autoimmune hypothyroidism, which around 90% of us with hypothyroidism do, then this can cause us to swing between hypo and hyper symptoms, causing intolerance to the heat and cold, so should you be having a Hashimoto’s flare from this, it can cause increased intolerance to temperatures.
To check for Hashimoto’s and to monitor how you are doing e.g. if it’s calming down, you need those two antibodies tests TPOab and TGab doing. You can read how to better control it here. Find out how to order your own testing here.
Also a part of the same system (the endocrine system) are your sex hormones, which often work in tandem with your thyroid hormones.
When one goes wonky, so can others.
Sex hormone imbalances coming hand in hand with thyroid problems seem to be increasingly common, so testing your progesterone and oestrogen levels is often very helpful. If a doctor won’t do this for you, you can arrange it yourself. If you’re of a particular age, considering the menopause or perimenopause would also be a good idea for your heat intolerance symptoms.
The adrenal glands are also part of the endocrine system and many thyroid patients find that they develop adrenal dysfunction on top of thyroid disease.
Adrenal fatigue (note: it is more accurately referred to as hypothalamic-pituitary axis dysfunction) seems pretty common among thyroid patients and testing for it with a 24 hour, four point saliva test will show if you do indeed have it.
When I had high cortisol adrenal fatigue, it was causing me to have hot flushes where I became unbearably hot and sweat buckets. Even in December!
What you need to keep in mind about your thyroid, is that it’s basically your body’s thermostat, regulating body temperature. But when you have a thyroid problem/thyroid heat intolerance, it won’t adjust or adapt to colder or warmer external temperatures like a regular person’s, which means you can struggle in the heat. Or the cold.
As well as taking into consideration the above info and exploring them, some of these tips may also help you to cope with feeling overwhelmingly hot.
- Take a cool shower before bed to cool down and remove sweat and stickiness.
- Replace a heavy duvet with a light sheet.
- Spray your bed sheets in cold water so that as you lay on them, they’ll slowly dry but help keep you cool in the process.
- Drink cold drinks, preferably water, with ice.
- You can also suck on ice cubes to help you cool down and hydrate at the same time.
- enjoy ice lollies and ice cream!
- Applying bags of ice cubes, ice packs or frozen peas to your wrists, back of neck and feet can also help cool you down.
- Consider investing in a fan or air conditioning at home, especially in the warmer rooms of the house and your bedroom so that your sleep is affected as little as possible. You can also try placing bottles of frozen water behind or in front of fans for a cooler breeze.
- Keep curtains and blinds closed during the day to keep heat out.
- Use cotton bed linen and clothing as it is breathable and allows ventilation.
- You can also stick your bed sheets in the fridge or freezer (in a bag) for 5 minutes or so before bed, to cool them down, too.
- Look at investing in a Chillow.
- Wear lighter colours such as white that reflect sunlight and avoid black and dark colours which can ‘absorb’ some heat and make you feel warmer.
- Wear loose fitting clothes for ventilation.
- Snack on frozen fruit.
- Run your wrists under cool water.
What other tips would you add? Let me know in the comments below.
You can click on the hyperlinks in the above post to learn more and see references to information given.
Rachel Hill is the highly ranked and multi-award winning thyroid patient advocate, writer, speaker and author behind The Invisible Hypothyroidism. Her thyroid advocacy work includes writing articles, authoring books, producing her Thyroid Family email newsletters and speaking on podcasts, as well as being a founding board member for the American College of Thyroidology. She is well-recognised as a crucial contributor to the thyroid community and has a large social media presence. Her books include “Be Your Own Thyroid Advocate” and “You, Me and Hypothyroidism”.