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Thyroid Hormone T3 and its Relationship with Happiness

hypothyroidism thyroid hormones thyroid issues
hypothyroidism depression Thyroid Hormone T3 and its Relationship with Happiness thyroid hormone t3 triodothyronine liothyronine sodium elle russ blog post hypothyroidism happiness woman in field spring

When I had low levels of thyroid hormone T3 in my body (Triiodothyronine), I could barely think, I was depressed, and it was an awful mind and body to exist in. It felt like my brain was in a fog - similar to having a stuffy head when all you can do is stare into space, and nothing seems like fun. Other symptoms include impaired memory, inability to focus, and a sense of being paralyzed in terms of motivation. I had over 30 symptoms due to untreated hypothyroidism.

I continually thought to myself, “What the heck is wrong with me?” I felt as if I was completely aware of my lack of motivation, but I still couldn’t seem to do anything about it. In comparing lab work to symptoms, I have noticed that if my Free T3 drops to a certain level, I inevitably become depressed, overwhelmed, unfocused, and unmotivated, and other cognitive issues arise, such as saying words incorrectly or jumbling up their pronunciation. I also experience physical symptoms like constipation, inflammation, and weight gain.

Our brain cells have thyroid hormone T3 receptors, and adequate amounts of T3 (via natural T4 to T3 conversion or direct thyroid hormone dosing) are critical for proper brain function and the development of both newborns’ and adults’ brains. Untreated hypothyroidism in adults is associated with cognitive defects along with balance and motor skill issues. Brain-to-hand dexterity issues can result in messy handwriting. Speech can be affected - not being able to find the words to say, or saying words backwards/mispronouncing words...words you have been speaking your entire life. The effects of low levels of T3 in the brain feel very scary. When I was suffering with low T3, I recall thinking, "Am I getting dumber? Something is happening to my brain." 

Thyroid disorders have been closely linked to psychiatric disorders, and patients are often misdiagnosed with depression or bipolar disorder without understanding that one of the causes can be low levels of T3. Patients diagnosed with depression, anxiety, or bipolar disorder should be tested by doctors for thyroid issues to determine whether the cause is inadequate levels of T3 (or too much T3). T3 interacts with brain receptors and crafts the brain’s sensitivity to neurotransmitters involved with memory, alertness, focus, emotions, and disposition.

T3 is an essential hormone that helps regulate the body's metabolism, energy levels, and mood. People with hypothyroidism often report feeling less happy and less satisfied with life. On the other hand, high levels of T3 can also lead to a condition known as hyperthyroidism, which is characterized by symptoms such as weight loss, nervousness, and irritability. People with hyperthyroidism may also experience mood swings, making it difficult for them to feel happy and content. The high levels of T3 can also cause an increase in heart rate and anxiety, which can further negatively impact a person's mood and overall well-being.

Maintaining proper T3 levels can help ensure that the body is functioning optimally, which in turn can positively impact a person's mood and overall happiness. T3 affects neurotransmitters, which are the chemical messengers in the brain responsible for transmitting signals between nerve cells. T3 plays a role in regulating the levels of neurotransmitters such as dopamine, norepinephrine, and serotonin, which are associated with mood regulation, motivation, and overall well-being. Low T3 levels can decrease the levels of these neurotransmitters, causing symptoms such as depression, fatigue, and decreased motivation. On the other hand, high levels of T3 can cause an increase in the levels of these neurotransmitters, leading to symptoms such as anxiety and nervousness.

What to look for in lab results

In the United States, the Free T3 reference range on lab tests is usually 2.0 - 4.0 (In Canada it could be 3.0 - 6.0) People who have no hypothyroid symptoms and are not taking thyroid hormone replacement usually have a Free T3 result in the middle of whatever range your country uses. For example, the average Free T3 result for the USA range of 2.0 - 3.0 is 3.1. However, people on thyroid hormone replacement could have a higher Free T3 result. People who are metabolically and calorically efficient with low body fat (like athletes) might have a lower-than-midrange Free T3 result without hypothyroid symptoms...I refer to these types as "T3-Efficient" - their bodies need less T3 hormone to run on, versus the average person. 

Getting a comprehensive thyroid panel is critical if you are experiencing hypothyroidism symptoms. Low T3 levels wreak havoc on the human body - as our thyroid gland is the master gland of the human body and the thyroid controls the production and regulation of sex hormones, the regulation of body temperature, heart rate, and more.

Talk with your doctor about getting this comprehensive thyroid panel:

  • TSH
  • Free T3
  • Free T4
  • Reverse T3
  • TPO ab (Thyroid Peroxidase Antibody) *Hashimoto's Disease
  • TG ab (Thyroglobulin Antibody) *Hashimoto's Disease

About the author:  Elle Russ is the #1 bestselling author of The Paleo Thyroid Solution, a world-renowned thyroid health expert, and a master coach. Take her FREE Thyroid Masterclass HERE


  • A study published in the "Journal of Affective Disorders" found that patients with depression had lower levels of T3 compared to healthy controls. 
  • Another study published in the "Journal of Clinical Psychiatry" showed that patients with major depression had lower T3 levels and that the severity of depression was positively correlated with the decrease in T3 levels. 
  • The National Institute of Mental Health (NIMH) provides information on depression and its relationship with other medical conditions, including low levels of T3. 
  • The American Thyroid Association provides information on the role of the thyroid gland in mental health, including depression.

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