Old cat.

[AniaSM]

I'm worried about my female cat. She is now 12 years old. Her fur on her back and her back legs have become thin and she eats very little. Also she sleeps almost all the time in front of my fire.
It's very cold outside. Is her behaviour because it's winter or is she getting old?

[saanen]

She might have a thyroid problem which would explain the loss of fur, the poor appetite and the lethargy. You should take her to the vet for a check up.

[NancyBee]

I agree with saanen, it might well be thyroid, although at only 12 years old she is not old. Do get her checked as soon as possible. It might be her teeth, if she has some bad teeth, it will be too painful for her to eat and she will then obviously lose weight and be listless if she is not getting enough nourishment. Let us know how you get on.