Pituitary gland

The pituitary gland, also called the hypophysis cerebri, is an important endocrine gland found in vertebrates. In humans, it sits at the base of the brain, attached to the hypothalamus. This small gland plays a big role in controlling many body functions through the hormones it produces.

The pituitary gland is located in a little dip in the skull called the sella turcica, specifically in an area known as the hypophyseal fossa. It is about the size of a kidney bean, roughly 1 centimeter across and weighing just under one gram.

The pituitary gland has two main parts: the anterior lobe and the posterior lobe. The anterior lobe makes and releases several important hormones, while the posterior lobe stores and releases hormones that are actually made in the hypothalamus.

Hormones from the pituitary gland help control many body processes, including growth, blood pressure, energy use, how the sex organs and thyroid gland work, metabolism, and even aspects of pregnancy, childbirth, and breastfeeding. It also helps manage water and salt balance in the kidneys, body temperature, and even pain relief.

Structure

The pituitary gland is a small gland located at the base of the brain, sitting in a bony enclosure called the sella turcica. It is made up of three parts: the anterior pituitary, the posterior pituitary, and an intermediate lobe. The intermediate lobe is very small in humans but is more distinct in other animals.

The anterior pituitary produces several important hormones and is controlled by the brain area known as the hypothalamus. The posterior pituitary also releases hormones that are made in the hypothalamus and travel down a stalk connecting the two areas. Both parts of the pituitary gland play a key role in controlling many body functions through the hormones they produce.

Main article: Anterior pituitary

Main article: Posterior pituitary

Function

The pituitary gland, also known as the hypophysis, plays a key role in controlling many body functions by releasing special chemicals called hormones. The anterior part of the pituitary gland releases hormones that manage growth, stress responses, reproduction, metabolism, and milk production.

The posterior part of the pituitary gland stores and releases hormones that help control water balance in the body and support childbirth by helping the uterus contract. Together with the hypothalamus, the pituitary gland helps keep the body’s systems working smoothly.

Main article: Pituitary gland

Development

The pituitary gland forms early during the development of an embryo. It starts as a small group of cells in the outer layer of the developing body, called the hypophyseal placode. This group of cells forms a pouch called Rathke’s pouch, which becomes the front part of the pituitary gland. At the same time, a part of the developing brain grows downward to form the back part of the pituitary gland.

During the next few weeks, these parts change and move into place. The front part of the pituitary starts making important hormones like growth hormone around the 12th to 16th week. By the end of the first three months, the pituitary gland is fully formed and connects to the brain, helping control many body functions.

Clinical significance

Main article: Pituitary disease

The pituitary gland plays a key role in many body functions, and problems with it can lead to various health conditions. For example, not enough of a hormone called vasopressin can cause a condition known as central diabetes insipidus. Too much growth hormone in children can lead to gigantism, while too much in adults can cause acromegaly. Other issues include hypothyroidism from low levels of thyroid-stimulating hormone, as well as over- or under-production of pituitary hormones, known as hyperpituitarism and hypopituitarism. Pituitary adenomas, which are usually non-cancerous tumors, can also affect the gland's function. The pituitary gland helps the body respond to stress and its size can be influenced by early life experiences and hormone levels.

History

The pituitary gland has an interesting history. Ancient Greek physician Galen called it gland and thought it helped produce nasal mucus. Later, anatomist Andreas Vesalius named it glandula pituitaria, which means "gland in which slime drips." This is where the name pituitary gland comes from.

The term hypophysis was created by German anatomist Samuel Thomas von Sömmerring. It means "under growth" and refers to the gland's position below the brain. Over time, scientists learned more about its real functions.

Other animals

The pituitary gland is found in all vertebrates, but its shape and structure can vary a lot between different animal groups. In mammals, the pituitary has a specific shape, but in other animals like lungfish, amphibians, reptiles, and birds, it looks quite different. For example, in lungfish, the pituitary is a flat sheet, while in birds, a certain part of it is missing.

In fish, especially those that are not lungfish, the pituitary looks even more different. It often has a well-developed part called the intermediate lobe. Some fish, like lampreys, have a simple form of the pituitary that might show how it first evolved in ancient vertebrates. There are also interesting structures in other animals, like a gland in armadillos that is similar to part of the pituitary, and even a structure in octopuses that works in a similar way.

Additional images

The following images help show the pituitary gland and related structures:

• Frontal view
• Pituitary and pineal glands
• Depiction of pituitary gland