When it comes to achieving optimal health, most people with thyroid and autoimmune thyroid conditions don’t think much about the importance of their liver. And when we do think of the liver, we tend to focus on its role in detoxification. This of course is an extremely important function, and perhaps THE most important function. However, there are numerous other functions of the liver, and this organ has a role in thyroid health, which I’ll discuss in this post.
Understanding Some of The Many Functions Of The Liver:
Before I discuss the role of the liver in thyroid health, I think it’s important to understand some of the more important overall functions of the liver.
1. Removes or excretes drugs, hormones, and other substances. The liver is well known for its role in detoxification. There are many different toxins in our environment, and it’s the job of the liver to transform these toxins into less toxic compounds, and then assist in the excretion of these compounds. I’ll expand on this shortly when I talk about the different phases of detoxification and biotransformation.
2. Involved in carbohydrate metabolism. The liver plays an important role in maintaining glucose concentrations in a normal range (1) [1]. The liver stores glycogen, and this allows the liver to remove excess glucose from the blood and store it, and then when the blood glucose concentrations begin to fall it will release glucose back into the bloodstream.
3. Involved in fat metabolism. The liver plays a big role in lipid metabolism, as the formation of most lipoproteins (molecules made of both protein and fat) takes place in the liver. Cholesterol synthesis also takes place in the liver, and the conversion of carbohydrates and proteins into fat occurs in the liver.
4. Involved in protein metabolism. The deamination, or breakdown, of amino acids mostly takes place in the liver, as does the formation of urea. Deamination of the amino acids is required before they can be converted into carbohydrates or fats. Urea helps to remove ammonia from the body fluids. Formation of the plasma proteins also occurs in the liver.
5. Stores certain vitamins. Some of the vitamins stored by the liver include vitamin A, vitamin D, and vitamin B12.
6. Plays a role in vitamin D metabolism. I have spoken numerous times about the importance of vitamin D, and how this is deficient in many people. The liver produces 25-hydroxy vitamin D, which is the most abundant circulating form of vitamin D, and its measurement is used to assess vitamin D deficiency (2) [2]. As a result, if someone has problems with the liver, this can lead to low levels of 25-OH vitamin D. However, most cases of vitamin D deficiency aren’t caused by liver problems, as liver function needs to be severely compromised in order for the synthesis of 25-OH vitamin D to be impaired.
7. Involved in blood clotting. The liver is responsible for the formation of numerous substances which are important for the coagulation (clotting) of the blood. This includes fibrinogen, prothrombin, Factor VII, and other coagulation factors. As a result, acute and chronic liver conditions can lead to decreased synthesis of clotting and inhibitor factors, decreased clearance of activated factors, quantitative and qualitative platelet defects, hyperfibrinolysis, and accelerated intravascular coagulation (3) [3]. Simply put, problems with the liver can cause problems with blood clotting.
The Phases of Biotransformation and Detoxification
With regards to the toxins we’re exposed to, there are three phases involved in the biotransformation and detoxification of these compounds. In Phase 1, foreign compounds are converted into either more potent or less potent compounds in preparation for Phase 2. In Phase 2, the metabolites produced in phase 1 are combined with other substances which make them less toxic, and they also become more water soluble so they can be excreted through the bile and urine. Phase 3 involves the excretion of these compounds.
Something called Cytochrome P450 plays an important role in biotransformation, as the CYP1, 2, and 3 families are responsible for the biotransformation of most foreign substances including 70-80% of all drugs in clinical use (4) [4]. Expression of each CYP is influenced by a unique combination of mechanisms and factors including genetic polymorphisms, induction by xenobiotics, regulation by cytokines, hormones, during disease states, as well as sex, age, and other factors (4) [4]. Certain factors such as eating cruciferous vegetables can help to increase the levels of these cytochromes. On the other hand, other factors can lead to a decrease in these cytochromes, and therefore have a negative effect on biotransformation and detoxification.
What Role Does The Liver Play In Thyroid Health?
The two main types of thyroid hormone are thyroxine, also known as T4, and triiodothyronine, known as T3. Although the thyroid gland produces about ten times more T4 than T3, the active form is T3. While the thyroid gland does synthesize some T3, this hormone is also produced through the conversion of T4 to T3. And 30 to 40% of this occurs in the liver (5) [5].
Many people reading this are already familiar with the role of the liver in converting T4 to T3, but the liver also plays a role in deactivating thyroid hormone. In addition, the liver also has specific functions with regards to thyroid hormone transport and metabolism. The liver synthesizes a number of plasma proteins that bind to the thyroid hormones and thereby provide a large, rapidly exchangeable pool of circulating hormone (5) [5]. Thus tissue thyroid status depends not only on thyroxine secretion but also on normal thyroid hormone metabolism, delivery of T3 to nuclear receptors, and on receptor distribution and function (5) [5].
So what does all this mean? Essentially it means that if someone has a liver which is not functioning optimally, then this can affect thyroid health. While it is true that most thyroid imbalances are due to the autoimmune component of Hashimoto’s Thyroiditis or Graves’ Disease, it would also be prudent to consider the role of the liver when it comes to thyroid health. For example, if someone has a problem with the conversion of T4 to T3, rather than just give the person a drug such as Cytomel, it probably would be a good idea to look into the health of the liver to see if this is what’s responsible for the conversion problem. Plus, as I’m about to discuss, one also needs to consider the impact of hypothyroid and hyperthyroid conditions on the liver.
Hypothyroidism and Liver Health. There is evidence that hypothyroidism may directly affect the liver structure or function, as it has been associated in a few case reports with cholestatic jaundice attributed to reduced bilirubin and bile excretion (5) [5]. Hypothyroidism might also result in the elevation of the liver enzyme aspartate aminotransferase (AST) (6) [6]. However, most of the people I work with who have hypothyroidism and Hashimoto’s Thyroiditis have normal liver function tests.
Hyperthyroidism and Liver Health. It’s not uncommon for people with hyperthyroidism and Graves’ Disease to have abnormal liver function tests (7) [7]. This includes alkaline phosphatase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma -glutamyltransferase (GGT), and total bilirubin. However, when these values are out of range due to the hyperthyroid condition, they usually revert back to normal once the thyroid hormone levels are normalized. One thing to consider is that taking antithyroid medication such as Methimazole or PTU can cause liver damage, and thus raise the liver enzymes.
What Can You Do To Achieve Optimal Liver Health?
The problem is that with all of the toxins we’re exposed to, the liver has to work extremely hard in the process of biotransformation and detoxification. Because of this you want to try to do what you can to optimize the health of your liver, and here are 3 main things you can do to accomplish this:
1) Eat foods that can help optimize the health of the liver. There are many different foods which can help detoxify the liver. Some of these include the cruciferous vegetables, garlic, and drinking green tea. For more information I would recommend reading a blog post I previously wrote entitled “3 Ways People With Thyroid and Autoimmune Thyroid Conditions Can Detoxify Their Body [8]“.
2) Do everything you can to minimize your exposure to toxins. Of course you want to try to eat as many organic foods as you can, as well as drink purified water. You also want to use natural cleaning products and cosmetics, as most name brand products are loaded with chemicals. If you frequently drink alcohol you should cut down on this, and of course want to avoid tobacco smoke. Regularly change your air filters, and consider investing in one or more air purification systems.
3) Do things to help eliminate toxins. Although minimizing your exposure to environmental toxins is important, you also want to do things to help eliminate toxins. One of the most important things you can do is to make sure you drink a sufficient amount of water each day. You also want to make sure you’re having regular bowel movements. These are the main two priorities when it comes to eliminating toxins, but there are other things you can do as well, such as taking nutrients or herbs to help with detoxification, or utilizing sauna therapy. Once again, you can refer to the blog post I wrote on detoxification for further information on detoxification.
So hopefully you have a better understanding as to why having a healthy liver is important for optimal thyroid health. With regards to thyroid health, having a healthy liver is important for both the activation and deactivation of thyroid hormone, as well as for thyroid transport. And of course most people realize the importance of the liver with regards to biotransformation and detoxification. But the liver also has other roles, such as the metabolism of carbohydrates, fats, and protein, and also is involved in vitamin storage, the synthesis of 25-hydroxy vitamin D, and in blood coagulation.