Endocrine System
The endocrine system is made up of the endocrine glands that secrete hormones. Although there are eight major endocrine glands scattered throughout the body, they are still considered to be one system because they have similar functions, similar mechanisms of influence, and many important interrelationships.
Some glands also have non-endocrine regions that have functions other than hormone secretion. For example, the pancreas has a major exocrine portion that secretes digestive enzymes and an endocrine portion that secretes hormones. The ovaries and testes secrete hormones and also produce the ova and sperm. Some organs, such as the stomach, intestines, and heart, produce hormones, but their primary function is not hormone secretion.
What does the endocrine system do?
The endocrine system is responsible for regulating a range of bodily functions through the release of hormones.
Hormones are secreted by the glands of the endocrine system, traveling through the bloodstream to various organs and tissues in the body. The hormones then tell these organs and tissues what to do or how to function.
Some examples of bodily functions that are controlled by the endocrine system include:
- metabolism
- growth and development
- sexual function and reproduction
- heart rate
- blood pressure
- appetite
- sleeping and waking cycles
- body temperature
What is a gland?
A gland is an organ that creates and releases substances that the body needs to function. There are two types of glands:
- endocrine glands, which release hormones directly into the bloodstream
- exocrine glands, like lymph nodes and sweat glands, which are not part of the endocrine system.
Organs in the endocrine system
The glands of the endocrine system are where hormones are produced, stored, and released. Each gland produces one or more hormones, which go on to target specific organs and tissues in the body.
The glands of the endocrine system include the:
- Hypothalamus. While some people don’t consider it a gland, the hypothalamus produces multiple hormones that control the pituitary gland. It’s also involved in regulating many functions, including sleep-wake cycles, body temperature, and appetite. It can also regulate the function of other endocrine glands.
- Pituitary. The pituitary gland is located below the hypothalamus. The hormones it produces affect growth and reproduction. They can also control the function of other endocrine glands.
- Pineal. This gland is found in the middle of your brain. It’s important for your sleep-wake cycles.
- Thyroid. The thyroid gland is located in the front part of your neck. It’s very important for metabolism.
- Parathyroid. Also located in the front of your neck, the parathyroid gland is important for maintaining control of calcium levels in your bones and blood.
- Thymus. Located in the upper torso, the thymus is active until puberty and produces hormones that are important for the development of a type of white blood cell called a T cell.
- Adrenal. One adrenal gland can be found on top of each kidney. These glands produce hormones that are important for regulating functions such as blood pressure, heart rate, and stress response.
- Pancreas. The pancreas is located in your abdomen behind your stomach. Its endocrine function involves controlling blood sugar levels.
Some endocrine glands also have non-endocrine functions. For example, the ovaries and testes produce hormones, but they also have the non-endocrine function of producing eggs and sperm, respectively.
| Hormone | Secreting gland(s) | Function |
|---|---|---|
| adrenaline | adrenal | increases blood pressure, heart rate, and metabolism in reaction to stress |
| aldosterone | adrenal | controls the body’s salt and water balance |
| cortisol | adrenal | plays a role in stress response |
| dehydroepiandrosterone sulfate (DHEA-S) | adrenal | aids in production of body odor and growth of body hair during puberty |
| estrogen | ovary | works to regulate the menstrual cycle, maintain pregnancy, and develop female sex characteristics; aids in sperm production |
| follicle-stimulating hormone (FSH) | pituitary | controls the production of eggs and sperm |
| glucagon | pancreas | helps increase levels of blood glucose (blood sugar) |
| insulin | pancreas | helps reduce your blood glucose levels |
| luteinizing hormone (LH) | pituitary | controls estrogen and testosterone production as well as ovulation |
| melatonin | pineal | controls sleep-wake cycles |
| oxytocin | pituitary | helps with lactation, childbirth, and mother-child bonding |
| parathyroid hormone | parathyroid | controls calcium levels in bones and blood |
| progesterone | ovary | helps prepare the body for pregnancy when an egg is fertilized |
| prolactin | pituitary | promotes breast-milk production |
| testosterone | ovary, teste, adrenal | contributes to sex drive and body density in males and females as well as development of male sex characteristics |
| thyroid hormone | thyroid | helps control several body functions, including the rate of metabolism and energy levels |