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The Thyroid/Gut Connection in Thyroid Disorders

The Thyroid/Gut Connection in Thyroid Disorders

The Thyroid/Gut Connection in Thyroid disorders

Our Thyroid gland is the most important gland in the body to regulate our metabolism (the rate at which we convert food into usable energy) and the regulation of various functions within the body.   Like all parts and systems in our body, it depends on the nutrients we derive from our digestion in order to function correctly and  maintain body balance.   Any disturbance of our gut will inevitably lead to a knock on effect to out Thyroid function and visa versa.

Thyroid Gland Function, Location And Disease
Thyroid gland is the largest endocrine gland in adult human. Endocrine glands are those that secrete their products directly into the bloodstream. In contrast, most exocrine glands release their secretions through a duct onto an epithelial surface such as skin or mucosa. Thyroid gland is made up of two lateral lobes joined together across midline by a narrow bridge of tissue called isthmus. It is relatively larger in women and children than in men.



Location Of Thyroid Gland



Thyroid gland lies in the anterior part of our neck, immediately below the larynx and overlying the trachea (windpipe). A normal thyroid gland weighs between 25 and 40 gm. This butterfly shaped gland is highly vascular so it receives one of the highest rates of blood flow per gram of tissue. Thyroid gland moves with the larynx in swallowing and speaking - this feature helps a healthcare professional to differentiate swellings in the glands from those in the adjacent structures.


Control Of Thyroid Hormone Secretions
Iodine is essential for thyroid hormone synthesis. Dietary intake of about 150 microgram per day mainly in the form of iodide is typical to maintain normal thyroid hormone secretion. In many countries common table salt is iodized to prevent iodine deficiency. Iodine deficiency is the most common cause of goiter which is considered as one of the thyroid diseases.
Thyroid hormones (TH) are secreted mainly in response to TSH (thyroid stimulating hormone) released from the pituitary gland. Pituitary which is also an endocrine gland located within our brain and attached to the lower surface of the hypothalamus. Secretion of TSH in turn is dependent on another hormone called TRH (thyrotropin releasing hormone) that is released from the hypothalamus.

Functions Of Thyroid Hormones
• Thyroid gland functions include the secretion of two major hormones T3 (also called Triiodothyronine) and T4 (also known as Thyroxine or Tetraiodothyronine). T3 is physiologically more active and more potent than T4. T3 and T4 are collectively called thyroid hormones (TH). Both are iodine containing amino acids. Thyroid hormones are anabolic in nature; anabolism pertains to the constructive phase of metabolism and is the opposite of catabolism, the destructive process of metabolism.
• Thyroid hormones cause increased heart rate, cardiac output and ventilation rate.
• T3 and T4 act on various target cells to increase oxygen consumption and the basal metabolic rate (BMR). BMR is the rate of energy expenditure in the body under basal conditions. Increased oxygen consumption and increased BMR lead to increased heat production in the body that in turn helps to compensate for increased heat loss in cold weather. BMR is usually measured 12 hours after eating and after a restful sleep in a comfortable temperature with no exercise or activity before the test. BMR is increased in individuals with hyperthyroidism which is a thyroid gland dysfunction. In hyperthyroidism, patients experience tachycardia, nervousness, muscle wasting and excess heat.
• Thyroid hormones increase glucose absorption from the small intestine and hepatic glucose production; however, patients with normal insulin concentration do not experience elevated serum glucose level.
• Thyroid hormones are essential for normal growth and maturation. They play crucial role in the development of central nervous system (CNS). The most serious effect of thyroid hormone deficiency during childhood is permanent brain damage and dwarfism.
• Thyroid hormones accelerate cholesterol clearance from the plasma.
• Thyroid hormones are required for conversion of carotene to vitamin A; patients with hypothyroidism may suffer from night blindness.
• Thyroid gland also releases a minor hormone called calcitonin which is involved in calcium and phosphate metabolism. Calcitonin stimulates cartilage growth and causes increased deposition of calcium in the bones therefore promoting bone formation and reducing calcium concentration from the blood.


How the Thyroid Gland is impacted by Your Digestion
Remember too much thyroid hormone is just as bad as too little. When thyroid dysfunction is overactive it’s called hyperthyroidism. There is a common hyperthyroid autoimmune condition called Graves’ disease. When there isn’t enough thyroid hormone, it’s calledhypothyroidism and the autoimmune condition is called Hashimoto’s thyroiditis. Either one of these scenarios affects the gut.

Much of what the studies focus on are constipation and diarrhea as a result of thyroid hormones affecting the following areas of the gut:

  • Digestive juice exertion
  • Rate and strength of peristalsis
  • T4 to T3 conversion
  • Gut flora’s role in level of thyroid hormone

There have been many studies showing that those with thyroid dysfunction are prone to developing specific GI issues.
For instance, those with Graves Disease were found to have 5 times the risk of developing Celiac Disease and there are associations with Graves and Crohn’s. And IBD has been connected with patients with Hashimoto’s thyroiditis.

Having a happy thyroid is so crucial to having a happy body, because the thyroid makes and secretes the hormones responsible for all this metabolism/digestive stuff. Thyroid hormones help turn the cogs of the great machine, so to speak. But to understand the root of why thyroid hormones are low or high, we first need to talk about the 2 common ones:  The Thyroid Hormones T4 and T3, which affect nearly all parts of digestion.

Meet Your Friends T4 and T3 (and How Your Gut Health Influences Them)
The thyroid gland makes T4 in response to the brain sending it a chemical messenger called Thyroid Stimulating Hormone (TSH). But most cells in the body want T3, which means this whole process gets complicated fast. When I say thyroid hormones I’m speaking about T4 and T3:

  • T4 – Tetraiodothyronine aka Thyroxine (think inactive form)
  • T3 –  Triiodothyronine (think active form)

T3 and T4 are made from iodine (notice: tetraiodothyronine) and can’t be synthesized without it. Produced directly by the thyroid, these hormones enter the bloodstream and are able to talk to all kinds of cells and help direct them in their jobs.
So, say that the thyroid has just squirted out some of its hormines, the majority of that hormone will be T4. This T4 actually gets converted into T3 in peripheral tissues. One of these peripheral tissues is THE GUT! As I mentioned above, T3 is the main hormone that the cells want and it’s easiest to think of T3 as the active thyroid hormone.
Many of the problems people have with thyroid hormones is in this conversion.

Conversion Is The Key
The conversion of T4 to T3 is not so simple; neither is the gut’s role in all of it. Conversion occurs in the kidneys, liver and gut, but it’s not just about what tissues are doing the converting. The health of the tissue and the enzymes involved in the conversion are vital. There are several enzymes, like Type I Iodothyronine 5’ deiodonase (5’-DI1), and micronutrients, like Selenium, that play a role in the process of converting T4 to T3.

Basically, there are a lot of steps in this process that could affect the amount of T3 produced. Scientists are still trying to uncover all of it, but they are finding that the gut may play a critical role in thyroid hormone regulation as well as in storing T3. And healthy gut flora have been found to assist in these T4 to T3 conversions, while bad bacteria have been shown to reduce plasma concentrations of thyroid hormones through endotoxin release.
To sum it up, a healthy gut and gut flora are important for converting T4 to T3 and to keep our cells happy and running properly.

Regardless of the health of your gut, if the rest of your body is producing too little or too much TSH, T4 or T3, then you might experience diarrhoea or constipation.
Is Your Thyroid Causing Diarrhoea or Constipation?
Diarrhea and constipation are typically never caused by one singular problem, so I’m not totally blaming the thyroid. What I am saying is if you’re someone who’s been eating SCD or Paleo, using lots of supplements and still seem to have motility issues then it could be because of your thyroid.

The research suggests that too much thyroid hormone (hyperthyroidism) in the body is linked more heavily to causing diarrhea. There could be several reasons for this diarrhea  including:

  • Fat malabsorption
  • Intestinal hypermotility
  • Hypersecretion of bile
  • Pancreatic enzymes and secretin in small intestine tissue
  •  And increased intestinal transit time

This is basically saying that your digestive system is running on high and this super speedy processing results in wasted food and loose stools.
In contrast, constipation is typically found in conjunction with hypothyroidism. This is thought to be due to slower intestinal peristalsis, which is the movement of food and waste through our intestines. If the cells that control this have a lowered metabolism due to less hormone signals, the waves are slower and/or less powerful. However, there could be other culprits as this paper points out.
And lastly, this study shows 54% of people with a sluggish thyroid also had SIBO, which may suggest that we should always be looking at these two at the same time.

Always Look at the Thyroid and the Gut?
Beyond the study above, why might we always want to look at this duo together? Well, it comes back to how systems work.
When we look at how parts of systems talk to one another, we always want to find the feedback loops. In the body, these are pathways of signals that feedback to other areas. For instance, we’ve already mentioned in this article that thyroid hormones affect how the gut moves, but the gut can also give signals back to the thyroid.
The two “talk” back and forth through many signals such as the conversion of T4 to T3 in the gut, gut flora and levels of inflammation in the gut. Let’s say, for example, you’ve got a bunch of inflammation from a parasitic infection (which reduces nutrients), the conversion of T4 to T3 can go down. Also, higher levels of inflammation could change the output of TSH from the brain. Furthermore, the gut’s ability to digest and absorb critical nutrients, like the Iodine and Selenium necessary for proper thyroid hormone health, is very important.

It’s the old chicken or the egg scenario; which one came first? And anytime we face this problem, the best thing to do is assume nothing and test and address both at the same time. A big mistake happens when Hashimoto’s or Graves’ patients don’t also pay attention to their gut.

How to Fix Your Thyroid and Your Gut (at the Same Time)
Great practitioners will be thinking about testing and supporting both of these systems at the same time.
After all, you’re the owner and manager of your body and ultimately responsible for your health.
In this practice we have greatly improved many clients who have Thyroid problems using this protocol.  Remember, Thyroxin is in inactive form of Thyroid Hormone and has to be converted to be of any actual use in the body.   But the bigger question has to be…why is my thyroid not making and secreting enough Thyroid Hormone in the first place?   The GUT!”
If you would like to vastly improve your health working with me in this integrative way, and benefit from the excellent results that are possible, please contact me on 02866328200 or email info@lindaburke.co.uk