Question: neither my mother nor myself respond to T3 supplementation (cytomel; up to 140 mcg/d). Body temp remains low and reverse T3 stays normal. Could you discuss the factors that might interfere with thermogenesis in response to T3, and offer considerations how to improve this?   Having normal levels of reverse T3 tells you that the body isn’t deliberately getting rid of the thyroid hormone. High reverse T3 would be a sign that your body just doesn't want the thyroid hormone around.   That doesn't seem to be happening and so that makes me wonder if there could be a problem with taking up the thyroid into the cells. In which case I would expect thyroid hormone levels to be higher in the blood then you would otherwise expect them to be.   Or if there's a problem with the thyroid actually carrying out its functions inside the cell to regulate gene expression. This could be a zinc deficiency issue, since zinc is necessary to allow the thyroid receptor to bind to the DNA. In fact, zinc is necessary for everything that has a nuclear receptor that alters gene expression by binding to a nuclear receptor. This includes receptors for vitamin A and vitamin D, receptors for the sex hormones, and for thyroid hormones; all require zinc to act.   But, you seem to be saying that your issue is a specific thermogenic response, which makes me ask, are you seeing every other thing that you would expect from thyroid  hormone and not thermogenesis?    If that's the case, I have no idea. But, if you're not seeing any of the effects from thyroid hormone that you would expect, then I would say maybe some kind of resistance to getting into the cell if blood levels are elevated. If blood levels are normal, then maybe it’s not acting on the nuclear receptor, which I'd think zinc deficiency.    I don't know what else you could do with the exception of measuring the free fatty acids, which would be high if you had a zinc deficiency. They might not be if you're taking insulin and you're eating moderate to high carb. Get free fatty acids measured, which would often be called NEFA, for non-esterified fatty acids.   You know you can't have everything. I would rather your pancreas just start making all the insulin it needs, but options are limited, right? so I don't know if you can fix the temperature issue. If you can with fixing it at the root problem great, but if you can't then absolutely I would I would manage your temperature with clothing.    This Q&A can also be found as part of a much longer episode, here:https://chrismasterjohnphd.com/podcast/2019/02/09/ask-anything-nutrition-feb-1-2019/    If you would like to be part of the next live Ask Me Anything About Nutrition, sign up for the CMJ Masterpass, which includes access to these live Zoom sessions, premium features on all my content, and hundreds of dollars of exclusive discounts. You can sign up with a 10% lifetime discount here: https://chrismasterjohnphd.com/q&a