One of my cats might have thryroid issues

[Malted Shark]

So....I took one of my 3 cats, Christmas, to the vet as she had been slowly losing weight and is pretty skinny at this point. Originally I thought it was because I was getting them both more active and because of the switch off of dry food way back when for my diabetic cat, Tip.

Well, it was that or hairballs that had been causing it. Vet is thinking thyroid, but I wanted them to just check for EVERYTHING. I figure a 1-time high cost is better than trying out every. Single. Option. Like what we did before coming to the conclusion that Tip was diabetic.

Anyways, I think food is important to note in this case? But I feed Special Kitty, yes, that walmart brand. Shoot me, but all of my pets require more important high priced items than better cat food. Like insulin is $250 every 5 months, Luka, my parakeet, needs frequent checks because she gets regular tumors, there's the tons of vet visits for Tip, there's this, there's that, I'm lucky if I have $1 left over at the end of the month caring for them. I figure, better job, better quality food.

But anyways, I've read a bit of info on thyroid problems in cats, but lay it on me. What changes might I need to make to the routine so I can brace myself for it?

[Keyona]

My aunt has thyroid issues, she has to take medication for it and if the dosage is wrong she is out of it for a while (Like she sleeps like no other) she also has weight issues.

A friend's dog growing up also had thyroid problems and was on medications and was always on the fatter side (I'm not sure if it was the meds or the poor care)

[Malted Shark]

Keyona

My aunt has thyroid issues, she has to take medication for it and if the dosage is wrong she is out of it for a while (Like she sleeps like no other) she also has weight issues.

A friend's dog growing up also had thyroid problems and was on medications and was always on the fatter side (I'm not sure if it was the meds or the poor care)

Hm....then I wonder why my vet suspected that because she's skinny?
Oh, also, I forgot to add some info. gonk She's 11, going to be 12 on Dec. 23rd(guess where she got her name from!), so getting up there.

So if it's a thyroid issue, looks like I'm to expect pills. Alright then, she's fairly good about that because she has seasonal allergies, so has to get some medicine for that during the summer.

[Malted Shark]

Also, my vet mentioned an enlarged something something dealing with one of her eyes....sorry it isn't descriptive, but she was mostly talking to herself about it and so used terms I couldn't understand. Could this be related?