What is the pituitary gland?
The pituitary gland is an endocrine (hormone producing) gland. It is one part of a special messenger system, helping to regulate a wide variety of the body’s functions. The pituitary gland helps to control your body’s functions by releasing hormones (special chemical messengers) into your bloodstream. These hormones are transported in your blood to their target. Here they usually cause the release of a second hormone. The target can either be specialised endocrine glands or other types of body tissue such as groups of cells.
The pituitary gland is often called the ‘master’ gland because it controls several other hormone releasing glands such as the ovaries, adrenals and testes.
Where is the pituitary gland found?
About the size of a pea, the pituitary is found at the base of the brain, behind the bridge of your nose. The pituitary is very close to another part of the brain called the hypothalamus.
The pituitary gland has two main parts: the anterior (front) pituitary and the posterior (back) pituitary. These two parts release different hormones targeting different parts of the body.
How does the pituitary gland work?
Your body is in a constant state of change. Your heart rate, blood pressure and body temperature all change in response to what you do and your surroundings. Your body has special systems that constantly monitor these and other vital functions. Not only must these systems monitor changes, they must also respond and help the body restore balance. One of these systems involves the hypothalamus and the pituitary gland.
The hypothalamus receives information from many sources about the basic functions of your body. It uses the information it receives to help regulate these functions. One of the ways the hypothalamus does this involves controlling the pituitary gland. The hypothalamus does this by using its own hormones to communicate with the pituitary.
Among the things monitored by the hypothalamus is the level of various hormones in the blood. The hypothalamus has special cells which receive information from the body indicating how much of each hormone is present in the bloodstream. When these hormones drop below a particular level this stimulates the hypothalamus to release hormones. These hormones travel to the pituitary gland, acting as the signal to the pituitary to produce one or more of its hormones. The hormones produced by the pituitary are released into the bloodstream. The bloodstream transports the pituitary hormones to other endocrine glands, such as the thyroid gland.
The pituitary gland hormones may then stimulate their target endocrine glands to produce their own hormones. These locally produced hormones do the actual work of regulating your body. For example, hormones produced by the thyroid increase the body’s metabolic rate. In some cases high levels of locally produced hormones stop the hypothalamus and pituitary releasing more of their own hormones. This principle is called ‘negative feedback’, and it prevents hormone levels from rising too high.
The anterior pituitary produces hormones that regulate a wide range of bodily activities from growth to reproduction. Whether a hormone is released by the anterior pituitary is governed by the hypothalamus. There are at least seven different hormones secreted by the anterior pituitary. The posterior pituitary produces just two hormones.
|The anterior pituitary makes and releases several hormones|
|Hormone released||Main target||Function|
|Adrenocorticotrophic hormone (ACTH)||Adrenal glands||Stimulates the adrenal glands to produce cortisol. Cortisol is important in controlling your metabolism, blood sugar levels and blood pressure. It is also an anti-inflammatory agent, and helps your body to resist certain stresses such as bleeding or fasting.|
|Follicle stimulating hormone (FSH)||Ovaries (women)
|Stimulates the ovaries to produce an ovum (egg) for fertilisation. Also causes an increase in the hormone oestrogen.
Stimulates the testes to produce sperm.
|Growth hormone (GH)||Many different cells of the body||The most well known effect in children is to increase height. In adults and children it helps to control the amount of muscle and fat in your body. It also helps to heal injuries and promotes your immune system.|
|Luteinising hormone (LH)||Ovaries (women)
|Triggers ovulation – the release of what will become an ovum (egg) ready for fertilisation.
Stimulates cells in the testes to produce testosterone
|Melanocyte-stimulating hormone (MSH)||Brain?||Exact role in humans is unknown. May influence brain activity, when too much is present may cause darkening of the skin.|
|Prolactin||Breasts||Together with other hormones prolactin stimulates the breasts to produce milk.
It is also found in women who aren’t pregnant. Men also have prolactin, but its function is not understood well.
|Thyroid stimulating hormone (TSH)||Thyroid gland||TSH stimulates the thyroid gland to produce its own hormones, triiodothyronine (T3) and thyroxine (T4).
These hormones help to control many bodily functions including heart rate, temperature and metabolism.
|The posterior pituitary makes and releases just two hormones|
|Hormone released||Main target||Function|
|Antidiuretic hormone (ADH)||Kidneys||Decreases urine production. (It causes more water filtered by the kidneys to be returned to the blood. This decreases the amount of urine.)
ADH also causes a rise in blood pressure.
|Oxytocin||Breasts and uterus||Stimulates contraction of the uterus (womb) during childbirth. Helps breasts to release milk.|