Another reason why I have RS2 resistant starch and soil based probiotics (very little is needed) in my ketogenic diet regimen as commensal gut microbes can convert inactive T4 into T3[1][2]?
Another indication your thyroid and gut bugs (they are starving to death) are out of whack (gut thyroid axis) is your swallowing reflex will act weirdly? (you want to keep swallowing or have an urge to do so for no apparent reason)
That’s when it gets really bad! For me that came with a pins and needles type numbness in my hands and feet! Talk about feeling strange, that will really get your attention on a scale of freaking-out; is a big fat 10!
Footnotes:
[1] “…I’m not going to discuss the exact mechanism of how thyroid hormone is produced, but most of the thyroid hormone that is produced is in the form of T4, while a small percentage of T3 is produced. T4 is mostly inactive, while T3 is the active hormone. So while a very small amount of T3 is produced by the thyroid gland, the rest of the T3 is produced in different parts of the body, with the liver responsible for a good amount of this conversion. However, in order to convert T4 to T3, the enzyme 5′ – deiodinase is required. And certain minerals are required to activate this enzyme. It’s Not All About T4: So while most medical doctors will prescribe T4, many times this isn’t enough to manage the person’s symptoms. But why don’t they recommend T3 as well? Some medical doctors do, many in the form of Cytomel, which is a synthetic brand of T3. Other doctors will recommend natural thyroid hormone, such as Armour or Nature-Throid, both of which consist of T4 and T3. Giving synthetic or natural T3 can help with the symptoms, but of course if the problem is that T4 isn’t converting into T3, then just giving the person T3 won’t correct this problem. The obvious goal in this situation is to correct the conversion problem, although it can be challenging to determine what is causing this problem. Here are some of the more common factors which can inhibit the conversion of T4 to T3: …More
[2] “…Bottom Line: If you are on a diet that lowers your insulin levels to the point where your liver cannot adequately make T3 out of T4, you are inadvertently doing damage to your thyroid by pushing your levels way too low. …” Dr. Alan Glen Christianson (Dr. C) is a Naturopathic Endocrinologist
(which I did! yay!l) figured I would deal with whatever came up. my total cholesterol is high at 239 but, I’m not worried about cholesterol. But my “thyroid function” came in low and will be retested at 6 months. I exercise hard (twice a day), lift and run. I have tons of energy 
I feast on weekends and special occasions. any thoughts on what’s up with this thyroid test? how could I have zero symptoms?