Glossary
Endocrine System
What is the Endocrine System?
The endocrine system is the body's network of hormone-producing glands and organs. Hormones travel through the bloodstream as chemical messengers, helping regulate growth, metabolism, reproduction, stress responses and homeostasis—the body's ability to keep internal conditions within a range that supports normal functioning.
Main Components of the Endocrine System
Hypothalamus
This small brain region connects the nervous and endocrine systems. It regulates hormone release from the pituitary gland, which sits below it and is connected by the pituitary stalk.
Pituitary Gland
The pituitary is often called the “master gland” because it controls several other endocrine glands, though it takes direction from the hypothalamus. Its anterior portion produces hormones involved in growth, reproduction, metabolism and stress responses. Its posterior portion releases oxytocin and antidiuretic hormone made in the hypothalamus.
Thyroid Gland
The butterfly-shaped thyroid sits in the neck. Its hormones regulate metabolism, growth and development. Too little thyroid hormone causes hypothyroidism; too much causes hyperthyroidism.
Adrenal Glands
These glands sit on top of the kidneys. Their hormones include cortisol, which helps the body respond to stress, and aldosterone, which regulates fluid balance and blood pressure.
Pancreas
The pancreas has both endocrine and exocrine functions. Its endocrine cells release insulin and glucagon, which help regulate blood glucose.
Reproductive Glands
The testes and ovaries produce sex hormones, including testosterone, estrogen and progesterone, that help regulate sexual development and reproduction.
What does the endocrine system do?
Hormones help coordinate processes that need to work together across the body: growth and tissue repair, energy use and storage, the reproductive cycle, and fluid and electrolyte balance.
Stress is a familiar example. Adrenaline, norepinephrine and cortisol help change the body's activity in response to a challenge, including changes in heart rate, blood pressure and available glucose.