Thank you everyone for the replies!
I have an added problem with hyperPARAthyroidism. High calcium distorts glucose metabolism, I think. Having had a thyroidectomy due to thyroid cancer (more than 20 years ago) makes things complicated too.
I will definitely try T3 on a regular basis now, taking 6 µg a day to see what happens. I tried it before but it was encorporated in a pill with T4 (Novothyral) and I could not adjust the dosage of T3. T3 comes from Italy and is expensive. I do not want to be insulin resistant (HbA1C of 6.0) Hope it helps with glucose metabolism and also with cholesterol which is really high (the ratio is still within limits). In a previous post someone pointed out high cholesterol can decrease with taking T3 (not statins, which I do not want to take).
Lifestyle factors? I do not eat sugar, am not overweight, do move on a regular basis. Do need carbs though. The only thing I can improve is eating less in between (but I am very often hungry), 62 kg for 1m70.
I am a bit worried about T3 and its effect on osteoporosis. I have -4.2, and have had 4 fractures in 8 years) but through the website I learned that low T3 is equally bad as high T3.
Maybe before I start I should have blood drawn (check for T3, cholesterol, glucose, calcium, parathyroid hormone a.o.) and then after a while again.
There is however not a single endocrinologist who is willing to help with follow-up. They just do not want to prescribe T3 (them bones!) and are not really knowledgeable about its effects. I had to press for Novothyral, but T3 no way.
I have a lot of digestive issues too (bloating, nausea, headaches from the hyperpara?), I suspect they could also have to do with histamine intolerance (how to test?) and lactose intolerance (tested positive).
I am just so fed up about how I feel, there are a lot of confounding issues (a.o. hyperPARAthyroidism) which make finding a solution really difficult.
Thanks again, it is so good to be able to get all this information through the website! Hope you are all doing as well as can be.