This document summarizes the key aspects of the endocrine system. It describes how hormones are released from endocrine glands into the bloodstream and act on target cells. The main glands and hormones are listed, including how the parathyroid gland uses parathyroid hormone to regulate calcium levels. The hypothalamus and pituitary gland help regulate hormone production through feedback loops. The pancreas maintains blood glucose levels using insulin and glucagon. While the nervous system uses electrical signals, the endocrine system relies on slower chemical messengers called hormones to maintain homeostasis. Diabetes occurs when insulin production or function is compromised, leading to high blood sugar.