Growth hormone 0.1ng/ml, acth 6pg/ml, adh (vasopressin) <0.5. Something wrong with my pitaury gland? Trying to find a reason for recently weird periods

Endocrinologist. These are not the typical hormones a doctor would test for irregular menstrual cycles. TSH, Proactin, LH and FSH are more typical. It sounds like you are seeing an endocrinologist already based on these tests. I would schedule follow up to over the results.