I am so very cold sensitive- especially this time of year. Why? I know that it has to do with my lack of a thyroid gland. Though I take medication for my " extreme hypothyroidism" as I call it, even the best medicine can not compete with a healthy, functioning thyroid gland. Before I discuss cold sensitivity that affects most thyroid cancer patients, I will provide a quick review of how the thyroid system works. And it is a system of different organs, so part of this concerns those of us who do not have a thyroid gland.
The thyroid system starts in our brain. The hypothalamus, which is located at the base of the brain, secretes a hormone called thyrotropin releasing hormone. It's friends call it TRH, for short. Friendly TRH travels from the hypothalamus down to see the pituitary gland, which lives about a block away from the hypothalamus. TRH stimulates the pituitary gland to produce TSH. If you are lucky enough to still have a thyroid gland, the TSH enters the blood stream, travels to the thyroid gland and stimulates it to produce T4. Since we are thyroid-less, we still get the T4 ( the inactive form) converted to T3( the active form) thanks to an enzyme called 5-deiodinase. Lucky for us, this enzyme is found in many tissues of the body. Here is an important fact to remember: " By far, most of the T3 in the body is produced from the conversion of T4 to T3 that takes place outside of the thyroid gland in the body's tissues." Our T4 comes from our medication, so that the process can be completed. In addition to taking T4, some people also take T3. It is interesting to note that T3 is approximately four times more active than T4. T3 is in fact, the physiologically active thyroid hormone. However, there is a delicate system of checks and balances. T4 is important because it provides a steady, constant supply of the T3. We need both, in other words. We can depend on our bodies ( thanks to 5-deiodinase) to metabolize our T4 to T3, or in some cases, we need additional supplementation with T3. This is an important subject for one to discuss with one's physician. In my humble opinion, thyroid medication choices should be individualized and no one size fits all.
I have reviewed how our thyroid system works; remember it is a system so that even though we are thyroid-less we still get to play in the game. I will now try to explain why the song " Baby it's cold outside" gives us the shivers, in more ways than one. In a study conducted by the Proceedings of the National Academy of Sciences ( PNAS) a previously unknown link was discovered between how thyroid hormone affects the blood vessels, and in turn, body temperature. Before this fact was discovered, and yes it involved mice, the cold sensitivity problem in hypothyroid patients was attributed only to the thyroid hormones overall effect on the metabolism in the cells. It is now known that thyroid hormones can influence how much dilation there is in blood vessels, resulting in how much heat is lost. So, cold sensitivity is a two-fer, involving cell metabolism and the amount of vascular dilation that occurs.
What do we do with this information? While it was interesting to learn about why hypothyroid patients and patients without a thyroid are more sensitive to environmental temperature, what can we do about decreasing this cold sensitivity?
First, make sure that one is taking the proper medication. Does the dose of T4 ( levothyroxine, Synthroid, Levoxyl and others) need to be increased? Could adding T3 (cytomel) be helpful? There is also the choice of a naturally derived product that contains both T4 and T3. There have been some potency and supply problems with this medication ( Armour thyroid, and others), so please keep that in mind if you and your physician choose this option. Your physician will do blood work to make sure that several tests are within range. TSH, free T4, T3 and others should be tested. Also, an important factor is how the patient feels. We are not just a set of numbers! How one feels on a certain dose or regiment affects one's quality of life. It is very important to choose a physician who understands this and is willing to " look beyond the numbers".
Getting enough sleep is so very important, also. When we rest, our body gets a vacation, of sorts. Sometimes if our medication is off, we do not sleep enough and/or get good, restful sleep. According to a study conducted by the Harvard School of medicine, blue light- from computers and even energy efficient lighting, can throw one's circadian rhythm out of order. Sleep will suffer, and worse, excessive exposure to blue light, particularly in the evening( when our bodies should be resting or sleeping) could be a contributing factor in causing cancer, diabetes, heart disease and obesity. Yikes! Exposure to blue light can suppress melatonin( a hormone that influences our circadian rhythms). I was unaware of this, but fluorescent lights as well as the popular LED lights produce more blue light than conventional lighting. Even a night light can produce blue light. ( a fact that is particularly upsetting to me!). Some ways that the Harvard study recommended to protect one from too much blue light include: using dim red lights for night lights(!); avoid looking at computer screens and cell phone screens approximately two to three hours before bedtime; expose yourself to lots of bright light during the day- which according to the study-boosts ones ability to sleep at night along with better mood and alertness during daylight hours; and finally, if one works the night shift, consider purchasing blue light blocking glasses.
Eating well, taking warm baths, wearing warm clothes, especially when one goes outside, are simple steps that one can take to help with cold sensitivity.
I have noticed that I am more sensitive to cold in the evenings. It may have something to do with the metabolism of my medications, perhaps that my pain threshold seems to be lower in the evenings, or something to do with my immune system. I am not sure exactly why this is the case, but in talking with other hypothyroid/thyroid cancer patients, several people feel more cold sensitive in the evenings as well. I could not find any studies on this, but there is probably one out there somewhere.
So, during this winter season, I hope that everyone, especially those of us without a thyroid, can stay as warm as possible. A friend of mine has recently switched to wearing all wool clothes this winter. She has wool dresses, leggings, sweaters, ponchos, even a pair of wool underwear. I think she may be on to something. I now have a wool hat and sweater. More to come, I hope...