I've Experienced Muscle Deterioration, Fatigue, Occasional Rapid Heart Rate, Hot

I've experienced muscle deterioration, fatigue, occasional rapid heart rate, hot flashes, hair loss. I had Grave's disease and radioactive iodine treatment years ago, so take replacement thyroid. I have psoriatic arthritis, moderate. Still, I am super thin (115 pounds, over 5'8". Tired much of the time. I know it's something, but what?