In this article:
Did you know that 14% of those diagnosed with hypothyroidism have narcolepsy? Narcolepsy affects your brain while hypothyroidism affects your thyroid gland. So, how can two very different medical conditions that affect different parts of your body be connected?
In this article, we are going to look at that connection. To help us understand the connection, let’s first get a better understanding of narcolepsy and hypothyroidism.
Narcolepsy is a neurologic condition where your brain is unable to control your sleeping and waking patterns. Because of this, people with narcolepsy will experience excessive daytime sleepiness. This is described as always feeling tired no matter how much sleep they get. Other symptoms that might be present include:
- Sleep attacks or sudden onset of sleepiness
- Cataplexy or temporary loss of muscle tone
- Sleep paralysis or the inability to move or speak while falling asleep or waking up
Cataplexy and sleep paralysis can last from seconds to minutes and will resolve on their own. A person with narcolepsy tends to fall asleep in the middle of an activity such as driving, talking, or eating. In between sleeping, people with narcolepsy are alert.
Types of narcolepsy
There are 2 types of narcolepsy: type 1 and type 2. In both types, people with narcolepsy will experience excessive daytime sleepiness. But the difference is that some may experience cataplexy while others will have low or normal levels of a hormone called hypocretin.
What is hypocretin?
Hypocretin also known as orexin regulates your sleep-wake cycle. Your hypothalamus, located in your brain, makes hypocretin and releases it into your brain and spinal fluid. Most people with narcolepsy have low levels of hypocretin in their spinal fluid. Because of this, researchers believe low levels of hypocretin cause intermittent wake and sleep states.
Thyroid hormone is essential for our growth and development, body temperature regulation, and metabolism. Every cell and organ in your body needs thyroid hormone to function. Four different hormones regulate the making and release of thyroid hormone.
Your hypothalamus releases thyrotropin-releasing hormone (TRH) which tells your pituitary gland to release thyroid-stimulating hormone (TSH). This signals your thyroid gland, located at the bottom of your neck, to release triiodothyronine (T3) and thyroxine (T4). These two hormones will circulate throughout your bloodstream. When the levels of T3 and T4 become low, your hypothalamus releases TRH and the cycle starts again.
Any changes in this cycle affect the release of thyroid hormone. Hyperthyroidism is when too much is released whereas too little is a condition called hypothyroidism. When your thyroid hormone levels are low, your body slows down because it doesn’t have enough to meet your body’s demands. Thus, causing symptoms of hypothyroidism.
While each condition has its own defining sets of symptoms, there are symptoms they share.
Besides sharing symptoms, narcolepsy and hypothyroidism have two other common factors.
- Hypothalamus involvement
- Autoimmune disease
Let’s take a closer look at these.
The hypothalamus connection
The hypothalamus, an area in your brain, produces hormones that control:
- Release of another hormone from other glands
- Body temperature
Two of these hormones your hypothalamus produces are hypocretin and TRH. To review, hypocretin regulates your sleep-wake cycle and TRH stimulates the release of TSH which ultimately leads to the release of thyroid hormones.
Even though the connection is not fully understood between hypocretin and thyroid hormones, current research suggests that one does affect the other. One study showed that people with narcolepsy had TRH deficiency. Thus preventing the release of TSH.
A 2005 study concluded that people with narcolepsy who had a low level of hypocretin also had low levels of TSH. Researchers believed this to be because sleep prevents TSH from being released. The longer you sleep the lower your TSH levels.
But, what triggers these changes in the hypothalamus, to begin with?
The autoimmune connection
An autoimmune disorder is where your immune system mistakenly starts attacking healthy cells in your body. This attack damages your cells, preventing them from functioning correctly. Having one autoimmune disorder puts you at risk of developing other ones. It is not unusual for someone to have more than one autoimmune disorder.
In narcolepsy, especially type 1, a decrease in hypocretin is due to the death or loss of hypocretin-releasing brain cells. Without enough hypocretin, your body will have trouble regulating your sleep-wake cycle. There is still a debate about what causes the death of the hypocretin-releasing brain cells. But evidence strongly suggests that it is due to an autoimmune disorder.
Hashimoto’s thyroiditis is a well-known autoimmune disease that causes hypothyroidism. It occurs when your body attacks your thyroid gland, destroying it. Because of this, your thyroid gland is not able to produce enough thyroid hormone. In response to low thyroid hormone levels, your body releases more TSH in the hopes that your thyroid gland will release thyroid hormone. But, your thyroid gland can’t because of the damage to it.
There are very few studies about thyroid hormone medications and the effect it has on symptoms of narcolepsy. Instead, most of the information comes from case reports.
In a 2014 case report a woman that had normal thyroid function had improvement in total sleep and excessive daytime sleepiness after starting levothyroxine. A pediatric case report showed improvement in sleep symptoms when thyroid replacement therapy was added to their narcoleptic medication regimen.
Knowing your thyroid levels is the first step to knowing if hypothyroidism is causing your sleepiness. Paloma’s convenient at home test is easy to use and will have your results back within days. Consider scheduling a virtual visit with one of Paloma’s thyroid practitioners to help you interrupt your results.