Common Health Issues

My cat, Ringo, is 13 years old, always an indoor cat. We noticed some aging in the past year. He has just lost bowel movement control & messing in the livingroom, dining area, bedroom. I took him to the vet today & he said that Ringo's thyroid was overactive along with a very high heart rate (240) which outside of being upset to be at the vet was way high. They took tests; we will hear, but that we may have to give Ringo meds from now on. Other options were a thyroid removal or a blast of iodine, neither of which are options to us. Does anyone have information to share?

My cat is about 18 years old ,she was on antibiotics for an infection and she had frequent upset stomach.After that her weight has been dropping of like a pound per month.The vet thinks she has a thyroid problem but she is VERY very frisky.I was just wondering if this weight loss was part of the aging process or should I be more concerned?