What Is the Pituitary Gland?
The pituitary gland is a small structure about the size of a pea which is attached to the base of the brain. It consists of four parts and is the most important gland in the body for it controls the hormone output of all the other ductless glands, including the thyroid and sex glands.
Hormones secreted from the pituitary gland help control: growth, blood pressure, and certain functions of the sex organs, thyroid glands and metabolism as well as some aspects of pregnancy, childbirth, nursing, and water/salt concentration at the kidneys, temperature regulation and pain relief.
Each of these hormones affects a specific part of the body (a target organ or tissue). Because the pituitary controls the function of most other endocrine glands, it is often called the master gland. The hormones produced by the pituitary are not all produced continuously. Most are released in bursts every 1 to 3 hours, with alternating periods of activity and inactivity.
Some of the hormones, such as ACTH, growth hormone, and prolactin, follow a circadian rhythm: The levels rise and fall predictably during the day, usually peaking just before awakening and dropping to their lowest levels just before sleep. The levels of other hormones vary according to other factors. For example, in women, the levels of luteinizing hormone and follicle-stimulating hormone, which control reproductive functions, vary during the menstrual cycle.
The pituitary has two distinct parts:
- Front (anterior) lobe, which accounts for 80% of the pituitary glands weight
- Back (posterior) lobe
The lobes are connected to the hypothalamus by a stalk that contains blood vessels and nerve cell projections (nerve fibers, or axons). The hypothalamus controls the anterior lobe by releasing hormones through the connecting blood vessels. It controls the posterior lobe through nerve impulses.
The pituitary hangs by a little stalk just behind the nasal passage and was named after the Latin word for “nasal secretion” by the Belgian Andreas Vesalius (1514-1564), known as the “father of anatomy”, who mistakenly believed that it discharged mucus into the nose.
If the pituitary is not functioning properly, gigantism or dwarfism may result. Premature old age, extreme thinness, extreme fatness and disturbances in sexual development are other disorders which may occur.