I'll bump this up for you since I think it is an excellent question; unfortunately, I don't know the answer but would like to. My T3 and T4 are mid-range but the frees are low normal...anyone know what this means or why this would be?
You might want to read up on goitrogens. Goitrogenic foods & env. goitrogens. Some goitrogens block uptake of iodine while others inhibit conversion enzymes. One textbook I've encountered on environmental goitrogens was close to 500 p. long. This is a huge issue, largely ignored by society because of our fixation on a pill-fix, a fixation that is nurtured by the pill profiteers.
Conversion enzymes are selenium based, so one needs adequate Se in diet for optimal conversion. Be careful w/supplementation; there is a narrow range of tolerance for Se; Se toxicity is nasty. I'm not saying don't do it, just be aware that too much Se can be much worse than too little.
Carbs tend to facilitate conversion in a person w/normal metabolism, but perhaps not so much in those suffering from metabolic syndrome, Syndrome X. A low-carb diet will have an impact on conversion.
Testosterone facilitates T4 conversion. That is one reason why men with high TSH often have fewer symptoms than women with the same numbers. Progesterone also facil. conversion, however it's not a huge factor w/males.
Adrenal function effects conversion as well as peripheral uptake of T3.
You could also read up on mitochondrial processes & efficiency, they're part of the package.
I am bumping this up again because I have a question. Can selenium be found naturally in foods or does it have to be taken as a supplement? Actually, I find this topic interesting because how many of you out there have had normal T3 and T4, never to be tested for free T3 or T4, only to find them low? How would a "normal" range T3 and T4 translate into a low FT3 and FT4? Is it truly as simple as selenium or is something else involved here? (or am I thinking too much and getting too deep? )
[QUOTE=sparkie;2795679] Can selenium be found naturally in foods or does it have to be taken as a supplement? Is it truly as simple as selenium or is something else involved here? [QUOTE]
Selenium is found in a variety of foods. Unblanched brazil nuts are an excellent source; one ounce can provide up to 3x the RDA for Selenium. Canned tuna -- 3.5 oz will give you 60 mcg.; 3 oz. of ground beef, about 30 mcg. There are many other foods that contain Se as well.
A low free T3 COULD be as simple as selenium deficiency. However, for many people in our modern world, those environmental & food goitrogens may play a role in damping conversion. There is increasing evidence being put forward by respected scientists that fluoride in water, food, juice, and dental care preparations, is bad for all of the enzyme systems in the body. In past, MDs used fluoride to block hyperthyroid.
There have been some reports that increasing Omega 3 fish oil (not O3 flax) improves thyroid function, though at the moment I don't recall whether or not it's a T4-T3 conversion-based influence.
And of course there are hormonal issues: progesterone & testosterone increase conversion, while estrogen generally binds TH but I'm not sure what it's effect on conversion, per se, is.