Rummikub (love that game!) ive had years of learning about it, having to get my head around it and suffering when it's not right. Also a member of the BTF which I recommend looking at if not joining.
T4 is levothyroxine, but it's a prohormone, our bodies actually use t3 for energy.
The very best explanation is in a book by the BMA by Dr Toft on thyroid disorders. I recommend anyone with an issue getting it, I've had to show my gp (and an endo) that sertaline was listed as a possible issue with thyroxine as well as the fact that most people need to be Tsh 0.5-2 max to feel well. Many gps do not do this. (Hence many would be pleased with the ops gp!) My info comes from here, mumsnet, BTA, btf, and I've read health unlocked with a careful pinch of salt. Much there has been helpful but there's also some unhelpful stuff. The toft book clearly says also that the ideal medication would be t4 with a little t3, but due to the different half lives this is tricky.
The bta and btf now embrace the eu recognition that some patients are better on t4 and t3. There's an excellent article by Dr perros from the freeman in newcastle however as to why t4 only is generally more stable IF Tsh is maintained. A few individuals simply do better with a little t3. He contributes to the btf magazines too.
What is really missing from all the mainstream advice (but has been carefully listed here and is on healthy locked) is that we need good ferritin, b12, folate and vit d. Imo unless pernicious anaemia is an issue (b12 - often associated with hypothyroidism) ferritin and vit d are most likely to be deficient in women, esp after pregnancy as it can drain both. And apparently it helps with t4-t3 conversion (I'm not sure about this science) but from my basic understanding and experience, you need ferritin/ iron for muscle growth. Thyroid issues impact lean muscle mass. If your iron is lagging there's no way your body can fully recover with good thyroxine levels quickly. I've seen studies which indicate hypothyroidism and hyperthyroidism can sometimes affect ferritin levels. My endo did comment that my ferritin was a little low. (55 - not that low tbh) However, I only got treated for it due to terrible muscle itching and cramps (restless leg syndrome) that was a bit odd as far as I can tell!
On here and health unlocked I've seen that 70-90 is best for thyroid hormones to work well, my muscle symptoms have only stopped when I reached around 80. So from my own experience id concur with this.
Thyroid stuff has buggered my life up a couple of times as it was missed. I'm very slim. So knowledge to me is power! I think many people with thyroid issues feel low and unconfident anyway as a result of the condition. So it's extra hard to keep going to the gp and trust them.
I do find the body really can lag behind results for some months, possibly due to issues such as iron etc. Or it just takes time to rebuild everything.