Pituitary Gland

Pituitary Gland

The pituitary is a pea-sized gland that is housed within a bony structure (sella turcica) at the base of the brain. The sella turcica protects the pituitary but allows very little room for expansion.

The pituitary controls the function of most other endocrine glands and is therefore sometimes called the master gland. In turn, the pituitary is controlled in large part by the hypothalamus, a region of the brain that lies just above the pituitary. By detecting the levels of hormones produced by glands under the pituitary’s control (target glands), the hypothalamus or the pituitary can determine how much stimulation the target glands need.

Untitled design (19)
Untitled design (20)

The pituitary has two distinct parts

  • Front (anterior) lobe, which accounts for 80% of the pituitary gland’s 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 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 adrenocorticotropic hormone ( 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.

Pituitary: The Master Gland

The pituitary, a pea-sized gland at the base of the brain, produces a number of hormones. 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.

 

Hormone Target Organ or Tissue
Adrenocorticotropic hormone( ACTH) Adrenal glands
Beta-melanocyte–stimulating hormone Skin
Endorphins Brain and immune system
Enkephalins Brain
Follicle-stimulating hormone Ovaries or testes
Growth hormone Muscles and bones
Luteinizing hormone Ovaries or testes
Oxytocin* Uterus and mammary glands
Prolactin Mammary glands
Thyroid-stimulating hormone Thyroid gland
Vasopressin (antidiuretic hormone)* Kidneys
* These hormones are produced in the hypothalamus but are stored in and released from the pituitary.

Pituitary gland malfunction

The pituitary gland can malfunction in several ways, usually as a result of developing a noncancerous tumor (adenoma). The tumor may overproduce one or more pituitary hormones, or the tumor may press on the normal pituitary cells, causing underproduction of one or more pituitary hormones.