Triiodothyronine (T3) is the active form of thyroid hormones that affects most of the physiological processes in the body, including metabolism, digestion, and growth and growth and development. When your T3 levels are low, you may feel tired and cold, have slow digestion and constipation, and experience brain fog.
Your T3/Thyroid Hormones Can Tell You More Than You Think
People are often mistaken and think that if they feel tired or weak and their thyroid hormones are low then their thyroid is the cause of their problems.
Low thyroid hormones can contribute to feeling weak and tired, but they are not the main cause of your issues.
Rather, inflammation and oxidative stress are what is causing your fatigue/weakness AND your low thyroid hormones.
Using T3 as a Diagnostic
I use people’s T3 level as one indicator of subchronic inflammation and oxidative stress, especially in the liver, as that’s where 60% of T3 is made (another 20% is made in the gut).
I also look at TSH and T4 and if they’re normal and the person has low T3 then that is more likely to mean that oxidative stress and inflammation are high because TSH and T4 aren’t affected by inflammation and OS (1). (Of course, you want to rule out an autoimmune thyroid condition first.)
There are other causes as well such as a nutrient deficiency (see below). But it’s a good guess that your oxidative stress and inflammation load is high if you have low T3 (without an autoimmune condition) (1).
If your thyroid hormones/T3 are normal, however, it doesn’t mean you don’t have oxidative stress or inflammation. It only works one way.
Low T3 is Bad in its Own Right
Low T3 can contribute to weakness, fatigue and lowered performance, but usually isn’t the main cause of fatigue (orexin is).
Low T3 can also slow your digestive system and cause constipation.
Besides lowering performance, Low T3 has its own set of problems. It makes you 4X more likely to have heart disease , and both heart disease and low T3 run in my family.
Low T3 mostly to do with oxidative stress and inflammation, but low T3 can also increase heart disease risk on its own.
My History With Low T3
I’ve had low T3 for a while, but I haven’t checked it in a long time and I feel good.
I realized it would be good to have indirect measures of thyroid function – both for me and for clients.
I wanted to see if various interventions can raise my thyroid hormones and it’s not convenient to take a blood test.
Using Heart Rate as an Indicator of T3
If you’ve checked your free T3 and it’s normal, then you don’t need indirect indicators. This is for people who already have had a low T3 count in the past. Instead of checking your blood test daily, these indirect measures can be useful.
The best objective indicator of your T3 status is your heart rate. A high resting heart rate (over 80) means you have too much T3 and a low heart rate indicates low T3 (under 60).
The best way to check this is to take your pulse right before a blood test checking your T3 so that you have a baseline. You also want to to take it randomly and see what your average is. Then once you have an idea of this, your pulse will be a more accurate indicator of your thyroid status.
A resting heart rate between 55-65 is generally a sweet spot regarding general health – assuming you don’t have low T3.
You can very easily check this with a Pulse Oximeter. Sit down and relax and put your finger in. After 30 seconds, it will give you an accurate number.
Now don’t confuse one indicator as a smoking gun. Athletes tend to have lower heart rates (under 60) and I’ve found many supplements lower my pulse rate. Mine tends to vacillate between 50-65. When I am on a supplement binge, it’s usually in the low 50’s.
However, if you’re not an athlete and you feel like crap all day, a pulse rate of 55 may indicate low T3 (as well as potential oxidative stress and inflammation).
It’s actually unhealthy to have a high resting heart rate, especially over 70. Compared with men with rates of 50 beats per minute or less, those at 71 to 80 beats had a 51% greater risk of death. At 81 to 90 beats per minute, the rate of death was doubled – and over 90 it was tripled .
As you can see, you don’t want a high heart rate. I just like to use it as one indicator of T3 status.
Other Indicators of T3
Indicators of low T3:
You need to look at the whole picture.
- Low Heart Rate 
- Feeling Cold  – below 98 degrees….
- Fatigue 
- Constipation, slow digestion 
- Low libido 
- Poor appetite (and Weight gain) 
- Low Pregnenolone and High LDL  – anxiety, bad moods, and low motivation are indicators of low pregnenolone. T3 thyroid hormones convert LDL to pregnenolone. Unless you take pregnenolone, you won’t know what a deficiency feels like.
Indicators of high T3:
- High Heart Rate 
- Feeling hot  or have a high temperature (above 99 °F).
- Diarrhea/Quick digestion 
- Increased consumption of fluids and food 
- Osteoporosis – T3 stimulates osteoclasts, which leads to lower bone density 
- Low libido
The following image is a bunch of blood variables that are commonly tested (check your CBC). They can help you in knowing if you’ve got a hypo or hyperthyroid.
As you see, the RBC, hemoglobin, and hematocrit are a bit lower in hypothyroidism.
My Experiment Increasing Thyroid Hormones
I decided to do an experiment to see if natural methods for increasing thyroid hormones worked. I implemented various measures and within a day I realized it worked.
My resting heart went from 55 to 95. I normally have no issue with bowel movements, but it felt like I was close to having diarrhea.
My body heated up and it felt like I had a fever. I felt my pregnenolone levels were high even without supplementing.
My bones also were hurting – probably because high thyroid hormones cause bone degradation.
Oddly, I felt tired and didn’t have an appetite. This was likely because high T3 was elevating inflammation.
How To Stimulate Your Thyroid
I use LLLT on my thyroid to stimulate it.
Irregular T3 Levels?
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