I'm sorry your cat is not feeling well, and would like to try to help.
I am going to go over hyperthyroidism, treatment options for that, and then a few things you could try to help your cat feel better.
As you probably know, Hyperthyroidism is a fairly common disorder of older cats in which the thyroid gland in the neck starts to over-produce a hormone called T4. T4 controls metabolic rate. So, the more you have of it, the faster the metabolism.
Cats that are hyperthyroid tend to eat voraciously, but lose weight because they burn the calories up so fast. Their heart rates increase, and the transit time through the intestines increases. So, they may develop diarrhea and vomiting, but not always.
Hyperthyroidism can be diagnosed by physical exam and blood and urine analysis. On a physical exam, I check for enlarged thyroid glands, and a rapid heart rate, and sometimes heart murmurs. Blood and urine tests allow a vet to confirm the diagnosis.
Hyperthyroidism responds really well to treatment.
There are 3 treatment options.
1. Methimazole given orally OR transdermally (a paste applied to the ear). This medication is given usually twice daily, always for the rest of kitty's life. As you have discovered, occasional cats don't tolerate the medication well. Your cat might have no problems with vomiting if she were given the medication by paste on her ear, though some cats will vomit with that as well.
Here is more about it: http://www.petplace.com/drug-library/methimazole-tapazole/page1.aspx
2. Surgery to remove the overactive thyroid gland. This is a tricky surgery, and not one that I have done myself. However, there are many older veterinarians who are very good at this surgery – as they had to be when we didn’t have other treatment options. The tricky part is that the thyroid is RIGHT beside the parathyroid. And while you can safely remove a thyroid gland, there can be serious consequences with blood calcium levels if you accidentally damage the parathyroid gland. So, you might have to look around for a vet who does this surgery. When I worked in California, my boss there did this surgery quickly and well. It cost about $500. Here is more about it: http://www.thepetcenter.com/gen/hth.html and here: http://www.sniksnak.com/cathealth/hyperthyroidism2.html
3. Radioactive iodine treatment (this last is the BEST treatment because it gives you a cure, but it is expensive). The cat has to spend about 1 week at a treatment facility that specializes in this service. In a perfect world where we did not have to consider cost, this would be the best option for almost every hyperthyroid cat! More here: http://www.radiocat.com/
So, as you can can see, there are a number of treatment options, though they might not be possible for your cat if she has other health problems as well.
Here is more about hyperthyroidism:
You have asked if your cat is in pain - and the answer is, fortunately, NO! I have spoken to many humans who have this problem (Graves disease in humans) and none of them report feeling pain. They feel restless and anxious, sometimes, but not in pain. I have never seen evidence of pain in cats either.
Quite often, cats with hyperthryoidism will have some degree of kidney problems as well. This can lead to them becoming dehydrated, which will then lead to loss of appetite. I am wondering if this might be what is happening with your senior cat.
What you can do is try to get some calories into her in liquid form - that way she is getting nutrition at the same time as fluids.
I suggest opening a can of tuna *in water* and offering her the liquid.
Also, you can pick up Clam Juice in most grocery stores (sold in with the V8 or with the canned tuna in my grocery store) and mix that with some water.
You could try Lactose Free milk (Lactaid is the Canadian brand).
Offer her some canned cat food, and mix it with water to make a slurry if she won't eat it.
Things you can do to encourage a cat to drink are:
- offer water from a very wide flat bowl as cats don't like their whiskers to touch the edges when they drink (which is why lots of cats like the toilet bowl).
- If she likes dripping water, leave a tap dripping for her.
- Offer bottled water and see if she prefers it.
- Offer chicken broth, diluted 50:50.
- See if she likes water with an ice cube in it.
- See if she likes it out of a cup or martini glass.
- Offer Whiskas Kitty Milk
- Offer her canned food as the first ingredient in water
- You could try getting some human baby food in meat flavours (check that there are no onions or garlic in the ingredients) and mix that with warm water and offer that, or syringe it in little bits into your cat's mouth. Beech Nut makes a line of baby food that has nothing but meat (beef, chicken, turkey or veal) in it.
Here's a link:
If you cannot find this, you could find another meat baby food - just read the label carefully to be sure there are no onions, onion powder, garlic, or garlic powder in it.
Try to get her to drink small amounts frequently. If you can, try syringe 1 teaspoon (5 mL) or liquids per half hour into her mouth.
I hope that these ideas help you to help your cat. If this has been helpful, please accept my answer and leave feedback. If you need more information, just click on reply and I will try to provide it!