Also remembered this old post from a member and thought you might like to read it.
"I was having some major problems with my metabolism. I am a nurse and I thoroughly researched all the scientific research on the internet and at the medical library. I, too was going to see doctors who would not help me. Fortunately, I found a doctor who gave me armour thyroid despite "normal" levels. I brought him a RMR test that showed my BMR in 750-900 range which is very low, I was cold all the time. I was fatigued. When you have to get in the tub 2-3 times a day to warm up your body, you got a problem I have fake nails and suddenly I wasn't needing to go as normally to have them filled they had really slowed in growth. I put together my own research on my body. I started taking the medication as prescribed and he adjusted accordingly until I was free of symptoms. I documented all the thyroid lab work before and after treatment. I went and had metabolic testing to test my bmr and it measured normal for my age and weight and I was symptom free. I then tapered myself off the thyroid and within 2 months all symptoms returned and metabolic testing once again was done, and BMR was extremely low. Back on meds. normal. You know your body best and I am not afraid to put the research in front of a doctor's face. The human body is not black and white."
Thyroid meds help only if your thyroid levels are too low and causing low metabolism. If thyroid meds are not needed, you feel worse by taking them, not better. If you are hypothyroid then taking doses to bring your Free T4 and Free T3 to optimal can be a significant improvement.
A few years back, Armour was taken off the market for a while due to a problem they had with the FDA, after they changed the filler material used in manufacturing the pills. During that time I had to resort to using T4 med again. Since my body was not adequately converting the T4 to T3 in about 8 or 9 months I gained 18 pounds, without changing anything else. As soon as Armour became available again, I switched back, and in about the same length of time I lost the 18 pounds, again without changing anything else.
Have a look at this information about calculating expected Basal Metabolic Rate.
English BMR Formula
Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in year )
.This formula suggests that for every pound gained, on average BMR goes up 4.35 calories per day. So, if for any reason your BMR dropped, say because of hypothyroidism, if nothing else changes, you will gain weight until the weight gain offsets the reduced BMR. So, say that you become hypothyroid and your BMR is actually 150 calories per day below the expected amount, for your weight, height and age. I think that means that over an extended period you would gain about 35 pounds (150 divided by 4.36) before the metabolic rate increase due to weight gain offsets the 150 calories per day we assumed due to hypothyroidism. I fully realize there are many other factors involved, but I think this illustrates that reduced BMR due to hypothyroidism can have a drastic effect on weight. And this doesn't even take into account that weight gain and lower energy from hypothyroidism may also reduce the motivation for daily activity, thus further reducing overall metabolic rate.