The Thyroid Hormone-Weight loss Connection

What does the thyroid do?

Your thyroid works in concert with your hypothalamus and pituitary to control your metabolism. When your thyroid receives a message from your pituitary in the form of TSH (thyroid stimulating hormone), it will take the mineral iodine and the amino acid tyrosine and turn them into thyroid hormones. These thyroid hormones control how your body produces heat and uses energy. 

Thyroid Hormone Conversion: 

T4 is the most abundant hormone, but T3 is stronger. The body must convert t4 to T3 as it is the only truly active thyroid hormone.  Most of this conversion occurs in the liver, but conversion also happens in the digestive tract and in other body tissues. 

Things that interfere with conversion:

• Stress
• Diabetes
• Acute injury
• Beta blockers and some other drugs
• Inflammation

The Functional Medicine Perspective on Thyroid Imbalance

• Endocrine disruptors: Chemicals like pesticides contain endocrine disruptors that can affect your thyroid hormone receptors, as well as your reproductive hormone receptors. They can even mimic your natural hormones! (1). This can result in low thyroid hormones as your body is not getting the message to produce more while these imposters are there.
• Environmental toxins: Since 60% of your thyroid conversion is done in your liver, if your body is overloaded by exposure to environmental toxins such as pesticides, chemical cleaners, paints, etc., your thyroid function is likely to falter. Your liver will be too bus keeping up its critical job of getting toxins prepared to exit the body and not have enough resources to convert as much of your thyroid hormones. 
• Food allergies: Eating foods that your body is sensitive to, intolerant of, or allergic to stresses the body. It causes inflammation and can interfere with your thyroid conversion as seen above. 
• Leaky gut: When your intestinal lining is permeable molecules that would normally not enter the blood stream due to their size can get it. Once your immune system spots these large molecules which should not be there, it rightly mounts an attack. Unfortunately, it is often your own tissues that are damaged in the cross-fire. Also, 20% of thyroid conversion happens in the gut. If the gut is inflamed and busy repairing itself, we can assume that it won’t be up to the task of doing its portion of the conversion.
• Nutrient deficiencies: There are 4 minerals that are crucial to thyroid function: iodine, selenium, magnesium, and zinc. A deficiency of the amino acid tyrosine could also some into play. The body needs both iodine and tyrosine to make thyroid hormones. A tyrosine deficiency can occur when someone doesn’t eat enough protein.

How the Thyroid Hormones affect Metabolism and Weight loss

As you saw above, the thyroid is the gland that covers metabolism. If it is under-functioning, or hypo, then weight gain will be a likely result because metabolism will be sluggish. 

Furthermore, if your body is overloaded with toxins and therefore unable to do the proper conversion of inactive T4 to the active thyroid hormone, T3, your thyroid will function poorly, resulting in a hypothyroid state. If that weren’t bad enough, those excess toxins will be stored in your fatty tissues like your stomach and thighs. If you try to lose weight while your fatty tissues are filled with toxins and your liver is overburdened with more toxins, your body will not let you do this. This is no betrayal on your body’s part. This is to protect you!! If you were to lose weight, your body (especially liver) would have to re-process all those toxins. Since the feat would be impossible, those newly released toxins would be stored in different fatty tissue. Guess what your brain is made of?? Fat! Your body does not want these toxins ending up in your brain. Just think of all the horrible symptoms that would happen if that occurred! Your body wants to safely hold on to your fat until your body has the capacity to process them properly. Thank you, body!

TSH and Weight Loss: 

TSH (thyroid stimulating hormone) increases when the body needs more thyroid hormone produced. If your TSH levels are high, this may mean that your thyroid is not producing enough thyroid hormones: it is underactive. When you don’t have enough T4, there is less raw material to convert to T3, the active thyroid hormone that helps you burn your calories and keeps your metabolism balanced. 

T4 and weight loss:

As stated above, T4 is the most abundant thyroid hormone, but it is largely inactive and must be converted to the active form, T3. This happens in the liver, the GI tract, and other body tissues. 

T4 can convert to something called Reverse T3 (RT3) instead of converting to active T3. RT3 is designed to block the effects of T3 when your body needs to store energy. Unfortunately, stress and chronic dieting, which is a type of stress to the body, increase RT3. Trauma, inflammation, toxins, infections, liver or kidney disfunction, digestive dysfunction, food sensitivities, and certain medications can all inhibit the conversion of T4.

Hypothyroid patients often have both high levels of RT3 as well as high levels of leptin. Leptin is the fat storage hormone for your body. Your fat cells secrete leptin; therefore, levels of leptin normally increase when your body accumulates fat. This is important because the rising leptin signals to your body that you have enough fat stored and to stop storing fat!

Unfortunately, disorders such as hypothyroidism (as well as diabetes and obesity) have a high incidence of leptin resistance. Once leptin resistance develops, the body does not get the message to stop storing body fat even though there is plenty of leptin. In fact, it receives the opposite message: The body is starving, store fat! Oh no! You can see how this can be a major impediment to weight loss. 

T3 and weight loss:

The T3 hormone not only produces energy and increases metabolism, but it can promote weight loss. If you have low T3, whether caused by low T4 production or a problem converting T4 to T3, the body will slow down your metabolism, which will likely result in weight gain. Once your thyroid levels are balanced again, weight loss is much easier as the body ramps the metabolism back up.

Lab Testing for Thyroid Hormone Imbalance

Be sure to ask your doctor to run a full thyroid panel as many traditional doctors only run one marker when testing for thyroid dysfunction. With a full thyroid panel, your doctor will not only be able to see if there is imbalance, but be able to discern the type of imbalance and therefore how to go about correcting it. 

Traditional Doctors’ interpretation versus Functional Doctors’ interpretation of a Thyroid Panel:

Traditional thyroid lab ranges for “normal” are wide and based on all the people who had their thyroid tested at that particular lab. A Functional doctor uses a range that is much narrower and is based upon healthy thyroid function for optimal health. 

A full thyroid panel and the functional ranges for optimal thyroid function:

• TSH: 1-2
• Reverse T3: 14.9-26.7
• Free T3: 3-3.25
• Free t4: 1-1.5
• T4, total: 7.5-8.1
• T3, Total: 90-168
• T3 Uptake: 27%-37%
• TPO antibodies: negative or positive
• TGB antibodies: negative or positive

Natural Strategies to Balance the Thyroid and Improve Weight Loss

• Eat a diet containing plenty of the four crucial minerals: iodine, selenium, magnesium, and zinc. Supplement with one or more of these if you and your practitioner suspect a deficiency. 
  Don’t go low calorie: While trying to lose weight, it is understandable that some people try to cut their calories. However, going low-cal can actually reduce the function of your thyroid even further (2)! Instead, focus on 3 meals a day with plenty of protein, healthy fats, and fiber to regulate your blood sugar. 
• Move your body with moderation: Many people finding themselves unable to lose weight or gaining weight unexpectedly assume that they are not getting enough exercise. While this may be the case for some, for others too much exercise can put their body into a catabolic state (where muscle tissue is breaking down rather than building up). Since muscle burns more energy than fat, this can put someone into a viscous cycle of weight gain even though they are working so hard to do the right thing!
• Eat high quality protein: Be sure you are getting plenty of protein, especially foods containing the amino acid tyrosine that your thyroid needs like grass-fed steak, pastured pork, and wild-caught salmon. 
• Stop putting toxins in your body: Get rid of the endocrine disruptors such as plastics and synthetic fragrance. Eat organic vegetables. Eat pasture-raised meat and eggs. Eat wild caught seafood. Consume grass-fed dairy products. 
• Support your liver: If you are not detoxing properly, your body has to store excess toxins in your fat. 
  Eliminate food sensitivities: not only can food sensitivities causes inflammation and wreaks havoc with your immune system and cause all sorts of annoying symptoms, they can also cause you to gain weight.
• Sleep: Sleep is not only important for taking care of your hypothalamus-pituitary-adrenal (HPA) axis as listed above, but also for detoxing. Your liver goes through a cleansing of sort between 1 and 3 am. If you are not sleeping at that time, then you missed that detox for that night. Since we already learned that 60% of our thyroid hormones are converted in our liver, the excess toxins left there will not only be impeding this all-important conversion, but also likely be stored in our fat. 
• Undergo a detox program while under the care of a practitioner: As you saw above, detoxing is no simple matter. After you have cleaned up your diet and your household, enlist the help of a practitioner to guide you through detoxing safely. 

https://pubmed.ncbi.nlm.nih.gov/16037129/
https://pubmed.ncbi.nlm.nih.gov/2341229/