IV Classification of hormones 1. Proteins and polypeptides, including hormones secreted by anterior and posterior pituitary gland pancreas(insulin and glucagon) parathyroid gland(parathyroid hormone) many others Insulin [51 amino acids10 IV. Classification of Hormones 1. Proteins and Polypeptides, including hormones secreted by anterior and posterior pituitary gland pancreas (insulin and glucagon) parathyroid gland (parathyroid hormone) many others