What is the hormonal system?

The hormonal system, also called the endocrine system, is a network of glands and organs in the body that produces hormones.

Several glands make hormones, including the hypothalamus, the pituitary gland, the pineal gland, the thyroid gland, the parathyroid glands, the adrenal glands, the pancreas, ovaries and testes.

Each gland makes one or more hormones. Hormones are important for almost all cells in the body to work. They influence the metabolism, growth and many other functions. Some hormones influence almost all cells in the body. Others only influence a small number of cells in specific organs.

Some glands ‘talk to’ other glands, telling them to release particular hormones. For example, the pituitary gland releases hormones that tell the thyroid gland, the adrenal glands, the ovaries and the testes to release hormones.

How does the hormonal system work?

When a hormone is released from a gland, it travels in the bloodstream through the body. It passes by most cells, but eventually reaches its target.

When it reaches its target, it attaches to a particular type of cell, known as a receptor cell. The hormone then tells the receptor cell to do something. It can make cells grow faster, release another hormone, absorb sugar from the blood, withhold water from the kidneys, or one of many other important functions in the body.

What are some examples of hormones?

Some examples of hormones are:

Growth hormone: This is released from the pituitary gland. It is essential for normal physical growth in children and for some functions in adults, such as fat and muscle mass.

Thyroxine: The thyroid gland (in the neck) converts iodine from the diet into thyroxine. This controls many functions of the metabolism, including temperature, heart rate and growth.

Cortisol: This is released from the adrenal glands (just above the kidneys). It is important for controlling blood pressure and for dealing with the body's response to stress.

Insulin: This is produced by islet cells in the pancreas. It controls blood sugar levels.

Oestrogen and progesterone: These hormones, released from the ovaries, are responsible for female body characteristics and for storing and releasing eggs.

Testosterone: This is released from the testes. It produces male body characteristics and sperm.

Find out more about the main endocrine glands and their hormones.

What medical conditions relate to the hormonal system?

The hormonal system can go wrong. Glands might produce too many or too few hormones, or the target cells might stop responding properly to the hormones.

Some common hormonal problems are:

• diabetes
• thyroid problems, such as hypothyroidism and hyperthyroidism
• Cushing's syndrome
• some fertility problems
• congenital adrenal hyperplasia

These problems are usually treated by controlling how much hormone the body makes. An endocrinologist (endocrine gland specialist) can help diagnose and treat the problem.