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endocrine system diagram

Major glands involved in the human endocrine system.

The endocrine system is a chemical "factory" responsible for manufacturing hormones which all play an important in a range of bodily functions.

The endocrine system regulates our weight, appetites and metabolism, raises or lowers our blood sugar levels, is responsible for normal growth and brain development, signals menstruation, and stimulates the production of sperm and ovaries in human sexual reproduction.

How does it all work?

Endocrine glands release more than 20 major hormones directly into the bloodstream where they can be transported to cells that have built-in receptors to receive them.

The major glands that make up the human endocrine system are the hypothalamus, pituitary, pineal, thyroid, parathyroid, pancreas, adrenals, and the reproductive glands, which include the ovaries and testes.

Pituitary gland
About the size of a pea, the pituitary gland, located at the base of the brain just beneath the hypothalamus, is considered the most important part of the endocrine system.

However, the pituitary gland is actually controlled by the nearby hypothalamus, which transmits information sensed by the brain - such as outside temperature, light exposure, and even our emotional state - to the pituitary.

Perhaps the most well-known function of the pituitary is the production of "feel-good" chemicals called endorphins that have a major effect on our mood and sensitivity to pain. The pituitary also signals the ovaries and testes to make sex hormones, controls ovulation and the menstrual cycle, produces growth hormones that stimulates bone and body tissue development, and activates the thyroid to produce hormones that effect the adrenals.

Pineal gland

Located in the middle of the brain near the pituitary, the pineal gland secretes melatonin, a hormone that is stimulated by darkness, and usually produced most actively as we sleep with a major influence on the body's circadian rhythm, or wake-sleep cycle.

Thyroid gland

The thyroid, located in lower neck, is the butterfly-shaped gland that produces hormones that regulate metabolism, or how fast we burn up food to produce energy. It's also a major influence on bone growth and brain and nervous system development in children.

Adrenal glands

Situated on top of each kidney, the adrenal glands have several functions including the production of epinephrine which increases our heart rate and "fight-or-flight" reaction when the body undergoes stress. The adrenals also effect our metabolism, the immune system, and sexual development and function.


Although most associated with the digestive system, the pancreas also produces the hormones insulin and glucagon, that have a major effect on raising or lowering glucose (sugar levels) in the bloodstream which helps boost our daily energy levels.

Ovaries and testes

The main source of hormones involved in sexual reproduction, the ovaries and testes are also most associated with regulating body changes during puberty and the development of the sex organs.

In females, the ovaries produce eggs and the female hormone, estrogen, which is responsible for breast development, and regulation of the menstrual cycle. Another hormone produced by the ovaries, progesterone, also helps regulate the menstrual cycle and helps prepares the lining of the uterus for egg implantation.

In males, the testes secrete androgens, one of which is testosterone that controls sexual development and enlargement of the penis, production of sperm, as well as growth of facial and pubic hair and deepening of the voice during puberty.

Endocrine system and health

Since the endocrine system plays such an important role in so many different bodily functions, keeping it working properly simply comes down to giving the body what it needs - proper diet and nutrition, plenty of water, fresh air and regular exercise.

Cutting down on carbs and sugar will also help ward off such rampant diseases as diabetes, which occurs when the pancreas is overtaxed by superhuman demands on insulin levels, rising in response to processing all those sweets, chips, and junk food!

Stress is another major factor that influences all major functions in the human body with sometimes debilitating effects on the thyroid glands - such as hyperthyroidism or hypothyroidism - which can dangerously speed up or lower metabolism and heart rate.

also see in Health -> Diabetes Causes & Risk Factors | Thyroid Cancer

More about the endocrine system around the Web:

Endocrine System - Wikipedia
- Complete overview with information and diagrams explaining the glands, organs, chemicals and hormones involved in the endocrine process with related references and resources.

Endocrine System - Take the complete tour provided by Colorado State University.

Endocrine System Diagram - Interactive diagram leading to detailed information on the inner workings of the pineal, pituitary, adrenal, testes and thyroid glands.

Endocrine Diseases - Check out an excellent guide from MedlinePlus with clear descriptions of diseases and conditions effecting the thyroid, adrenal glands and pancreas with related diagrams, photos and illustrations.

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