The Relationship Between Mitochondria and Thyroid Health

The mitochondria have a number of important functions in a cell, and the most well known function involves the production of Adenosine triphosphate, which is also known as ATP.  In fact, most of the ATP is generated inside of the mitochondria.  ATP is created from the breakdown of carbohydrates and fats, and involves a process known as oxidative phosphorylation.  The goal of this post isn’t to discuss in detail the function of the mitochondria, but instead is to demonstrate how important they are to one’s thyroid health, and overall health as well.

But why is ATP important?  In addition to its well established role in cellular metabolism, extracellular ATP and its breakdown product adenosine exert pronounced effects in a variety of biological processes including neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation and liver glycogen metabolism (1).  ATP also plays an important role in DNA and RNA synthesis (2).

Certain coenzymes are important for the formation of ATP.  In order for these coenzymes to work efficiently, they require an adequate supply of certain nutrients.  This is one of the many reasons why eating well is extremely important to one’s overall health.

Although the mitochondria are essential for life, they constitute the greatest source of reactive oxidants.  They also contain heavy metal ions such as iron and copper, and all of this favors the formation of free radicals.  Free radicals are molecules with unpaired electrons, and in this state they are very reactive and can cause damage to our cells.  Fortunately the body produces antioxidants to help prevent free radical damage, and of course many people get antioxidants in the food they eat and/or the supplements they take.

The primary cause of cell death is a depletion of cellular ATP.  Mitochondrial function does deteriorate as one gets older.  It was proposed that the maximal life-span is mainly an expression of the genetic control over the rate of oxygen utilization, and that the rate of mitochondrial damage produced by free radical reactions increases with increasing oxygen consumption, which ultimately causes cell death (3).  So while oxygen is of course necessary to survive, aerobic metabolism is what leads to the formation of these free radicals.

Other Factors Which Lead To Mitochondrial Damage

As I mentioned earlier, free radicals are produced by the mitochondria.  So essentially the free radicals produced by the mitochondria are responsible for their own damage.  How does this happen?  Well, during oxidative phosphorylation, normally all of the oxygen consumed is converted in mitochondria to something called the superoxide radical.  Superoxide is then transformed to hydrogen peroxide by certain enzymes.  When these enzymes are unable to convert the superoxide radical to hydrogen peroxide, this causes oxidative damage.  Mitochondrial damage in turn can lead to the development of inflammatory mediators, such as tumor necrosis factor alpha.

One also needs to keep in mind that certain nutrients are important for the mitochondria to function normally.  As a result, if someone eats a lot of refined foods and sugars, thus resulting in a deficiency of those nutrients important for mitochondrial function, then this can result in mitochondrial decay (4).

Certain toxins can also cause mitochondrial damage.  For example, one study showed that thimerosal-derived ethylmercury (which is used as a preservative in certain vaccines, skin test antigens, and tattoo inks), inhibits mitochondrial respiration and leads to an increase in the formation of superoxide (5).  The study found a five-fold increase in the levels of oxidant damaged mitochondrial DNA after Thimerosal treatment.

There is also evidence that certain pathogens can cause damage to the mitochondria.  For example, one study showed that Clostridium difficile can cause damage to the mitochondria (6).  However, this was conducted on hamsters, and it is unknown if the same effect takes place with humans.  There is also evidence that an H. Pylori infection can cause mitochondrial damage (7)

The Importance of Thyroid Hormone For The Health of The Mitochondria

It has been known for a long time that thyroid hormones act directly on mitochondria, and thereby control the transformation of the energy derived from oxidations into a form utilizable by the cell (8).  Those with hypothyroid conditions consume oxygen more slowly because the mitochondria respire slowly.  On the other hand, those with hyperthyroid conditions consume oxygen faster because the mitochondria consume oxygen faster.

One study I came across discussed how hyperthyroidism is associated with tissue oxidative injury (9).  In other words, hyperthyroidism can lead to an increase in mitochondrial damage.  However, the same study discussed how thyroid hormone can activate mitochondrial mechanisms which provide protection against tissue dysfunction.  So while having an excess amount of thyroid hormone isn’t a good thing for the health of the mitochondria, having healthy levels of thyroid hormone can help to protect the mitochondria from damage.

Another study I came across looked at the effect of thyroid hormone on the mitochondria (10).  The article discussed how thyroid hormone status has a profound impact on mitochondria, and that thyroid hormones stimulate mitochondriogenesis and increase cellular oxidative capacity.  So what this is saying is that thyroid hormone is important for the formation of mitochondria, and also increases the cells capacity to utilize oxygen.

How To Improve The Health Of The Mitochondria

I recently attended the International Conference on Human Nutrition and Functional Medicine, and they dedicated an entire day discussing how to improve the health of the mitochondria.  One of the presenters was Dr. Matthew Hirschey, and he spoke about how caloric restriction can help to improve the health of the mitochondria, which in turn can increase lifespan.  This has not yet been proven in humans, although it has been proven with many different species of animals.  So while one wants to eat well, it also is important not to overeat, which of course many people have a tendency to do.

During the presentation Dr. Hirschey spoke about how Okinawa, Japan has the world’s longest life expectancy, and a low rate of chronic health conditions which are related to the aging process.  Although genetics can play a role in this, Dr. Hirschey also mentioned how they tend to eat until they are 80% full, whereas it’s common for people who live in other countries (including the United States) to eat until they are close to 100% full.  This of course is common when going out to eat, as many people will start off with a high carbohydrate appetizer, have a big meal, and even though they are stuffed will “make room” for dessert.

Regular exercise is also important for optimal heath of the mitochondria.  It seems that an age-associated decline in mitochondrial function contributes to insulin resistance in the elderly (11), and studies have shown that there is a robust improvement in skeletal muscle mitochondrial content and function in response to an achievable program of moderate intensity physical activity (12). Another journal article discussed how the cardioprotective effects of exercise might be mediated, at least partially, by redox changes and include the up-regulation of mitochondrial chaperones, improved antioxidant capacity, and/or elevation of other protective molecules against cellular death (13).  More research needs to be done in this area, but the evidence is strong that engaging in moderate exercise on a regular basis improves the health of the mitochondria.

Certain nutritional supplements can also help to improve the health of the mitochondria.  Some of these include Acetyl-L-carnitine, CoQ10, resveratrol, lipoic acid, and omega 3 fatty acids.  This doesn’t mean that everyone should take all of these.  While I recommend for just about everyone to take an omega 3 fatty acid supplement, not everyone needs to take these other supplements I listed.  However, I do think it’s worth reading a blog post I wrote entitled “CoQ10 and Thyroid Health“, as many people with thyroid and autoimmune thyroid conditions have depleted CoQ10 levels.   There is also evidence that improving the vitamin D status of those with a vitamin D deficiency can help to improve mitochondrial oxidative function (14).

To summarize these findings, thyroid hormone is important for the health of the mitochondria.  As a result, someone with a hypothyroid condition will have problems with the production of ATP.  Remember that ATP is important for energy production, and so a decreased production of ATP can lead to a decrease in energy, which is quite common with hypothyroid conditions.  But as I mentioned earlier in this post, ATP is also important for proper neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation and liver glycogen metabolism.  And so having a hypothyroid condition can affect all of these functions. On the other hand, a hyperthyroid condition can lead to an increase in mitochondrial damage.  Some of the factors which can help to improve the health of the mitochondria include caloric restriction, regular exercise, and taking certain nutrients such as magnesium, fish oils, the B vitamins, vitamin C, lipoic acid, and CoQ10.  Obviously taking supplements isn’t a substitute for eating well, as eating a diet consisting of mostly whole foods while avoiding the refined foods and sugars is essential for optimal mitochondrial health.