There could be so many contributor of fatigue for dialysis patients and would be too much to list in one post based on what I have read and learned (the hard way). I am still learning.
I know when I was on in-center dialysis 3 days a week, I was exhausted! I lost 45lbs of muscle mass, half my head of hair, and most of sense of taste. The cause of fatigue can be dialysis related or another underlying health condition. You mentioned checking out your thyroid function. You might want to check instructions for taking your basal body temperature which you can do to further help you determine if you have a thyroid issue. Selenium, L-tyrosine and iodine are nutrients your thyroid needs to produce hormones. The amazing herb Ashwaganda, which post contributor Timer mentioned in one of his posts, supports the thyroid function and provide stamina. Look up its health benefits, you will be amazed. I would be very careful with iodine though. Your doctor can order a simple urine test (if you still urinate) to check to see if you are deficient and can prescribe you the right dosage.
As for dialysis related fatigue causes (again too many to mention in one post), I would make sure you are getting in all the right amount of proteins and B vitamins. Both are depleted during dialysis. If you are on Hemo dialysis the estimate is that you loose 15-20g of protein per treatment! Your body will get it from your muscles if you are low and you will loose muscle mass. Ask me how I know. And remember just because you are consuming enough proteins does not mean you are digesting it. So if your digestion is comprimised then your absorption of nutrients is too. If you suspect that this migh be the cause, then you might want to check into amino acid supplements and probiotics (to help digestive health and absorption of nutrients). Below is a link with information regarding other dialysis related fatigue causes:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2582327/Good luck, excuse my spelling and grammer mistakes as I am running late for an appointment.