This leaflet gives a brief overview of the pituitary gland and the hormones it makes.
What is the pituitary gland?
The pituitary gland is a gland in the brain which produces chemicals called hormones (an endocrine gland). Hormones are chemical messengers which help different organs in the body communicate with each other. The pituitary gland is one part of a messenger system. The pituitary gland helps to control your body's functions by releasing hormones 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 sometimes called the master gland because it controls several other hormone-releasing glands. Some of the glands the pituitary gland controls are the thyroid gland, the ovaries, the testicles (testes) and the adrenal glands.
Where is the pituitary gland found?
About the size of a pea, the pituitary gland is found at the base of the brain, behind the bridge of your nose. The pituitary gland is very close to another part of the brain, called the hypothalamus.
The pituitary gland has two main parts:
- The part of the pituitary gland at the front, called the anterior pituitary.
- The part of the pituitary gland at the back, called the posterior pituitary.
These two parts release different hormones which are aimed at different parts of the body.
There is also a section between the two main parts, called the intermediate part, which releases a single hormone. The final part of the pituitary gland is the stalk, which connects the posterior pituitary to the hypothalamus.
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 systems that constantly monitor these and other vital functions. Not only must these systems monitor changes, they must also respond to the changes and help the body to restore balance.
Some of these systems involve the hypothalamus and the pituitary gland. The hypothalamus and the pituitary gland are part of several loops or circuits. The loops include other glands. The hormones produced by each gland complete the loops by travelling in the bloodstream between them.
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 gland.
Among the information 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 gland to produce one or more of its hormones. The hormones produced by the pituitary gland 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.
Take the example of the control of thyroid hormones from the thyroid gland in your neck. The hypothalamus produces a hormone called thyrotropin-releasing hormone (TRH). TRH travels to the pituitary gland and stimulates it to release thyroid-stimulating hormone (TSH). TSH travels to the thyroid gland and stimulates it to release thyroid hormones, T3 and T4. When levels of T3 and T4 get high enough, levels in the bloodstream are detected by the hypothalamus. The hypothalamus then knows to stop releasing more TRH. This last part of the loop is called negative feedback and 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|
Testicles (testes) - men
|Stimulates the ovaries to produce an egg (ovum) 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 the body. It also helps to heal injuries and it promotes your immune system.|
|Luteinising hormone (LH)||Ovaries - women|
Testes - men
|Triggers ovulation - the release of an egg (ovum) ready for fertilisation.|
Stimulates cells in the testes to produce testosterone
|Melanocyte-stimulating hormone (MSH)||Brain (not known for sure)|
The exact role in humans is unknown. It may influence brain activity. When too much is present, it may cause darkening of the skin.
This is also produced in the intermediate part of the pituitary gland.
|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 reduces the amount of urine.)|
ADH also causes a rise in blood pressure.
|Oxytocin||Breasts and womb (uterus)||Stimulates contraction of the womb during childbirth. Helps breasts to release milk.|
Some disorders of the pituitary gland
Problems occur when the pituitary gland is either too active or not active enough.
Conditions where the pituitary gland produces too much of one or more of its hormones include:
Conditions where the pituitary gland fails to produce enough hormones include:
- Adult growth hormone deficiency.
- Diabetes insipidus.
- Pituitary tumours.
- Tumours of, or injury to, the hypothalamus, having a knock-on effect on the pituitary gland.
Further more detailed information available free online
The Hypophysis Cerebri
From Gray's Anatomy Online
Human Physiology/The endocrine system
From Wikibooks, the open-content textbooks collection
There is also information available on the websites of the support groups listed below.
Dr Rachel Hoad-Robson
Dr Mary Harding
Dr Adrian Bonsall