Hyperthyroid and low potassium

My cat's initial symptom was constipation. Examination prior to teeth cleaning...basic blood work came back fine. After teeth cleaning 1/4 ib weight loss and muscle loss. Complete blood work showed potassium of 3.3 and CPK of 2707 and TSH of 4.7. No renal failure showing although my understanding is hyperthyroidism can mask renal problems. He's taking potassium gluconate 1/2 of 438mg tab twice a day for a week and 1/4 of 5mg methamazole once a day for 4 days so far. Is there anything else I should be looking for? His weight hasn't improved...never been a big eater. He's my love bug and I was even thinking of radioactive iodine if we can stabilize him. Afraid the 7 day hospital stay will stress him and make him sicker. I'm into holistic health and the radioactive procedure makes me nervous.
Thank you so much.

[Dan Sims, DVM]

All the advice you are receiving is sound but I would still treat with radioiodine.
Sometimes the specialist will discharge the cat before the 7 days are up.

[daisyfayis]

Thank you for your feedback. Is it also possible to get feedback from holistic vet? Not sure how this works but I will post comment to her as well. Thanks so much!

[daisyfayis]

I'm wondering If Dr. Cheng has any additional comments or opinion on radioiodine?
Thank you
Maria