@JoKalsbeek - I've been pondering your predicament a bit more, and I'll add a bit more context to my earlier contribution, to explain how I "see" how the thyroid works (or doesn't). However, a couple of things, if I may.
You didn't include your lab assay ranges with your levels? To be fair, thyroid levels seem to be fairly standard, with modest assay variations, but it's worth checking.
Secondly, you talk about hypo/hyper muddles up symptoms? Which hyp
er symptoms have you been experiencing?
As I understand it, with Hashi's sometimes this swinging around happens. I'm not hashi, so my reading around the specifics have been pretty high level, to be canded.
However, onto my vision of how the thyroid works.
TSH - is a signalling hormone, produced in the pituitary gland, to tell they thyroid to push out the theyroid hormone T4. It tells nothing more than how hard it is having to work, to get the thyroid into action. That's why, when this goes high, it can indicate the thyroid itself is sluggish, or ineffecient/effective.
Once diagnosed, the T4 we take each day allows the pituitary to relax, because the T4 is already present, by virtue of taking the tablets. One treatment for thyroid disease is in place, the value of TSH as a health marker is not quite meaningless, but it certainly should not be used to make any judgement on thyroid health. An exception to that would be if it continues to be very high, even with therapy in place.
T4 is a passive hormone. In itself, it doesn't do too much. In a natural state, our bodies, fiendishly clever things they are, gets on with converting the circulating T4, to make T3. This is where the exciting things happen!
T3 is the active hormone in he thyroid portfolio (although, T1 and T2 exists, it is unclear - to me anyway - exactly what they do). T3 is the magic that helps us feel better, reducing our symptoms and bringing our metabolic health back into line.
Without measuring T3 levels, nobody knows how well your T4 is actually working, and/or how well your body can convert T4 > T3. Obviously symptoms can be an indicator, but a lot of that is guess work.
Before the TSH test was discovered, all T4 dosing was done, based on symptoms, not data, but we are where we are now.
For some people, the conversion form T4 to T3 is very efficient, and they do well with just some oral T4, but for others, like me, their bodies can't for whatever reason, convert T4 to T3, so those people can end up on significantly higher doses of T4 than one might expect (based on a very rough rule of thumb, based on weight and age), with no significant impact on their T3 levels.
I reiterate, you really do have to eliminate all potential causes of this perfect storm of rubbishness you seem to be experiencing right now, but in your shoes, I would want to see an Endo who understand Hashi's and how fickle things can be if they have a flare.
Bearing in mind Hashi's is essentially an autoimmune condition, where the body sends out antibodies to attack the thyroid, that could be an explanation for your swollen, unhappy thyroid. This is what the NHS says about it:
https://www.nhs.uk/conditions/thyroiditis/#:~:text=Hashimoto's thyroiditis&text=As the thyroid is destroyed,to form in your throat.
Jo, I take from your initial post that you see less thyroid hormone as being a positive move. Thyroid hormones are a bit like insulin. A person needs what that person needs, and with Hashi's your needs can change from time to time.
I hope something in there might be helpful to you, but to be honest, Jo, I'd get myself over to HealthUnlocked and pretty much post your first post on there. If they do, they will ask for the assay ranges, to calculate how far into the ranges you are. Many people find they need to be well up in the ranges before they feel good.
They will also ask about vitamins and minerals I mentioned yesterday, because four our thyroids to work well, those levels need to be a in a decent place.
However, they are my massive learning resource for thyroid matters. My knowledge, although hard won, is still a the baby steps level, b comparison to those guys.
I feel for you. Get those ultrasound results and don't panic if they show nodules or whatever. Like many other unwelcomed lumps and bumps they can be perfectly benign, but obviously that has to be checked out.