Have had papillary thyroid cancer and total thyroidectomy ~1 year ago. TSH all in range. Still feeling very fatigued, hard time focusing. Going to get ACTH and Cortisol checked thinking adrenals?

Endocrinology. yes- get a full medical and endocrine workup and evaluation.
Other causes. Along with a full endocrine work up as suggested by Dr Miller, consider other causes. Have Vit d, Vit B, iron checked. Also have your sleep evaluated.
Get test done. There is possibility of other endocrines problem as it is well known with thyroid cancer.All your symptoms -as fatigue hard to focus need to be investigated by testing other endocrine gland functions .Hope every thing will be normal.