hooch-5, if you have the time read this article. There is some drop in Thyroid production but not metabolic rate, according to Dr. Greg Ellis. "Mostly it's calories that control the major metabolic rate changes and diet comp is involved, sometimes powerfully, but never anywhere near the effects of calories. Thyroid hormones do decrease with low cho but metabolism does not drop, interestingly."
http://www.dfhi.com/interviews/rosedale.html
its long, if u dont read the whole thing here is a section from it.
Thyroid-how does thyroid work? The thyroid produces mostly T4. T4 goes to the liver and is converted to T3, mostly there, other tissues too, but mostly in the liver. We are getting the idea that insulin controls a lot of what goes on in the liver, and the liver is the primary organ that becomes insulin resistant. When the liver can no longer listen to insulin, you can't convert T4 to T3 very well. Usually in people who are hyperinsulinemic with a thyroid hormone that comes back totally normal, it is important to measure their T3. Their free T3 will just as often as not be low. Get their insulin down and it comes back up.
Here are a few recommendations for keeping things running well.
Test for an iodine deficiency using a home test. swab a 3" by 3" solid square of 2% iodine tincture on your lower abdomen and leave it for 24 hours. If the orange square disappears before 24 hours u could benefit from iodine and the AA tyrosine supplementation, both help make T3. OR, (another test) take your body temp 4x a day for several days, before eating meals and before bed, and right upon wakening. Avg. the temperatures and if they read below 98 then there may be an issue as well.
Zinc and selenium help produce the enzyme that converts T4 to T3.
1/2 oz. raw nuts has a beneficial effect as well as warming effect to the body from its nutrients and EFA's. (walnuts are ideal b/c higher n-3 content)
Follow an exercise program predominantly anaerobic training, lifting heavy weights
Sunbathe 15-30 min a day (dont burn, obviously) The sun naturally steps the metabolism up by stimulation the throid to increase hormone production, studies on animals have confirmed this effect showing greater weight loss in those given sunlight exposure.
The throid will not shut down though, it will slow down conversion of T4 to T3. This is part of the equation but not the whole story. Also, eating as little as 50g carbs can allow less slowdown. Carbs need not be completely forbidden if this is a concern of yours. According to Dr. Rosedale too much carbs actually causes more of a problem as it interferes with the conversion of T4 to T3. Anyway, hope these suggestions help.