If you are hypothyroid and untreated.. that is stress enough for the adrenals. You don't have to have a lot of stress in your life to develop adrenal fatigue secondary to hypothyroidism. Because the thyroid is sub-par, the adrenals pump out more cortisol to try and compensate and finally just get fatigued.
'Twas news to me too, when I FINALLY got on Armour and started feeling good and then suddenly crappy. It was Janie and her mods who suggested adrenal fatigue. I got a 24hr saliva cortisol test done and BINGO! High cortisol aka adrenal fatigue. The longer adrenal fatigue goes untreated, the worse it gets and the more depleted the adrenals get (and untreated), eventually you end up with low cortisol and pretty much bed ridden.