How do you find out if they (adrenal adenomas) are functional or not?

Excess of Hormones: If the adrenal gland tumor/adenoma is producing excess of hormones, then it is called functional. The hormone levels can be easily measured in the blood and that gives us the final answer. Of course, the excess of hormones produces medical conditions which are well known to your doctor...they usually cause high BP and something called Cushing's Syndrome. Your doctor can explain it better.