My beloved 14-year-old cat Leeloo has been ill, losing weight rapidly, and was just diagnosed with severe hyperthyroidism. This can be fatal if not treated. Luckily there is very effective treatment (radioactive iodine therapy), but it, plus all the bloodwork she has and will need, are expensive. More info is in these posts: https://xenianth.tumblr.com/post/724491389822533632 and https://xenianth.tumblr.com/post/727935654067044352