My rat isn't eating: overgrown tooth? pituitary tumour? help!

Hi ! This is my very first post on here, and I hope you can help me! And sorry for the long post incoming;;

I've adopted an old rat a couple of months ago (because they weren't taking care of her too much on her previous home), and it's been all illenesess and trips to the vet since then... (she's 2 years old I believe)

She was super fat when I adopted her (she was being fed just with leftovers of the family) so I tried only giving her rat food.. which caused a huge weight loss, because she wasn't eating properly.
At first I thought she simply didn't like the new food; but I tried to make it more palatable for her (mostly adding a tiiiny bit of olive oil, which she adores) and she, at first, seems super interested on it, and goes stright to chew it as soon a she smells the olive oil... then she grabs a pellet (I have to cut them in very small pieces or she won't accept it) and tries to chew it but leaves it almost untouched. What I've observed is:

- She doesn't grab it. She used to do it when I first adopted her, but now she just leaves it on the floor and tries to chew it. I've read this can be due to a pituitary tumour (note: she can climb, so I don't think she doesn't have the strenght to just grab a pellet of food)

- Overgrown tooth. I can't be sure about it, because since she has been never handled much... I can't open her mouth (she won't chew tho, she's a sweetie). I think this may be it because, due her being a rodent, she should be chewing to prevent her tooth for overgrowing, but she hasn't been doing so. So, maybe that's a problem?

She will eat a liquid food the vet gave me; but I have to feed her manually and I don't have the time (it's 4 ml 3-4 times a day). I don't know what to do, that's the only thing she would eat!
Also, it's super expensive... does anyone know if baby food (or something similar) would do the trick as well?

So, have you ever seen something like this?
How did you solve it?

I've also tried to soften her food adding warm lactose-free milk, but she won't touch it :'c

Thanks!

Someone needs to examine her front teeth and her mouth, so if you can't then the vet needs to ...... overgrown teeth will grow through the side of a rat's mouth causing great pain and life threatening infection. Overgrown teeth need to be trimmed as the usual cause is that they no longer can be worn down properly because they no longer line up. http://ratguide.com/health/digestive/malocclusion.php

Here is some info on pt http://ratguide.com/health/neoplasia/pituitary_tumor.php If you hand her a cheerio or piece of puffed wheat, is she able to hold it in her front paws and eat it?
Does she head bump?
If she does have pt, there is medication that can help.

So she needs to see a good vet (knowledgeable & experienced in caring for rats) asap!

As for food, I don't know what you are feeding .... Harlan Teklad 2014 and Oxbow are the recommended blocks. Oxbow is available in most stores that sell pet food. Harlan can be ordered online.
You can continue to make the hard blocks available, but please also soak rat blocks in cold water to make mush and give her a dish of this mush at least twice a day so that it is always available ...... a little oli, as you mentioned, may make it more attractive to her.

In addition, give her daily vegs - such as baby kale, broccoli, cooked & mashed sweet potato, frozen/thawed peas or baby food peas, mixed greens, cooked & mashed squash, etc
and occasional heathy treats such as small pieces of fruit such as ripe banana, watermelon, berries, cooked oatmeal, cooked quinoa, organic pumpkin seeds if she is able to eat them, etc

In addition supplement her diet daily with organic soy infant formula (infant section of grocery store or pharmacy - and it needs to be the organic kind) thickened with a bit of baby cereal. She may also enjoy some baby food.

How is her breathing? Rats with resp. infections often lose weight as it is difficult to breath and eat at the same time .... without medical care and antibiotics they die gasping for air.

Are you using a water dish that can not be upset? Rats need to have at least 2 sources of water in their cage .... and she may be unable to drink from a water bottle, even if it looks like she is.
Hydration is essential as dehydration kills ... and since she isn't eating much, watching out for dehydration is very important. One way to tell if she is hydrated is to gently pull up on the skin on the back of her next and let it go. If the skin quickly snaps back into place then she is probably hydrated.

Does she live alone? Rats are social and need to live with at least one other rat.
She may be depressed and lonely.

Can you post a video of her eating and of her walking? pics?

Where are you located? Country, prov or state?

hope this info helps

I agree with SQ. If you can get us a video, we can maybe see better what's going on.