...and has started to pee on the newspapers that surround the litter box but still poops in the box. She is 15. Is this senility? I have tried 5 different litters with the same result so I went back to her original litter. No difference.
Not sure the inappropriate peeing necessarily has anything to do with senility, or hyperthyroidism for that matter. Have you had a urinalysis done on her urine? What does her blood work say, besides hyperthyroidism?
At 15, a urine check is warranted. If she is experiencing any pain when peeing, she will associate that with the box and not her body - which means she has no issues when pooping that would stop her from using the litter box for that.