Since as noted above Vitamin D is needed to best metabolize Thyroid. It is possible that this happened "all of a sudden" in January because of the lack of sunlight which your body uses to make Vitamin D. Due to colder weather, more clothing and less hours of sunlight per day.
My first thought when looking over were similar to Gimel. Low Ferritin "stuck out" at me. And also noted the lack of testing forVitamin D3, Iron and Vitamin B-12. Low in those and fatigue is also the primary symptom.
It is a bit odd that you have almost diameterically opposed thyroid resulsts. With FT3 being high, but FT4 being low. I have never really heard of "T3 pooling" but those test results would certainly be consistent with that theory.
I think there is an enzyme that helps "push" the FT3 into the cell. It is energy dependant. And it appears that this may be lacking possibly in you. Thus without the energy to push the T3 into the cell it would result in "pooling". So that could be the issue. I can't recall what you need to help with this enzyme off the top of my head. I may have to go back and read up on this to recall.
I don't know why it would change overnight, but you definitely have some issues with your thyroid hormone levels. I would start by supplementing with about 25 mg of one of the iron supplements I listed above and increase about every week or so until you get your ferritin up to about 70 minimum. When you re-test for ferritin, check your Free T3 and Free T4 again and let us know how you are doing. Along with the ferritin, you may want to take some magnesium to prevent the possibility of constipation from the iron supplement. There are a number of good magnesium supplements, but I don't recommend magnesium oxide.
Thank you! Can you tell me if something like this can just happen so suddenly? I was feeling great in the end of last year and then suddenly I started feeling so bad. It got worse over the course of a few weeks and now I barely get out of bed. Which is alarming because I'm usually an active and happy person. My doctor said that it is not necessary for me to take iron supplements but that I could try it if I feel tired - which I do. What dosage would someone usually take and for how long?
The concern I see in your blood test results is that your Free T3 is unexpectedly high. When this occurs, it can be a problem called "pooling of T3 in the blood". The available T3 is not getting into your cells and being metabolized as it should. This condition is reported to be due to having low cortisol levels. Low cortisol can be due to several potential causes, including low ferritin, as shown in scientific studies. Since your ferritin is much too low, this would be a good place for you to start. I'd suggest that you start supplementing with one of the good forms of iron, like iron fumarate, iron bisglycinate, iron sulphate, or iron gluconate. Your target would be to get your ferritin up to about 70, and allow some time for the change to affect your Free T3 levels.
In addition, a hypothyroid patient often finds that their Vitamin D and B12 levels are too low, which can cause hypo like symptoms, as well. Also, D needs to be high enough to effect good metabolism of thyroid hormone. D needs to be about 60, and B12 needs to be in the upper part of its range. So it would be a good idea to test for D and B12 and supplement those as needed.