What is the pituitary gland?

The pituitary gland is a small gland, approximately the size and shape of a pea. It is located between the eyes, behind the bridge of the nose, just below the brain. The pituitary lies within a bony depression in the skull called the sella turcica , which sits below the optic chia sm , the area where nerves from the eyes (the optic nerves) cross and enter the brain. It is often referred to as the “master” gland of the body, because it produces hormones (proteins that are released into the body that influence the function of other organs) that control several other glands throughout the body, including the thyroid gland, the adrenal glands, and the sex organs (ovaries and testicles). The pituitary gland is divided into two main portions: the larger anterior pituitary (at the front) and the smaller posterior pituitary (at the back). Each of these portions has different functions, producing different types of hormones. It is rare for tumors to develop in the posterior lobe of the pituitary gland.

The pituitary itself is controlled by another gland called the hypothalamus , which sits just above the pituitary gland. In response to various signals from the body, the hypothalamus sends hormones directly down a channel to the pituitary gland, telling the pituitary to produce and release its hormones into the bloodstream so they can act on various organs throughout the body.

What hormones are produced by the pituitary gland?

In the posterior lobe, two different hormones are produced:

Anti-diuretic hormone (ADH, also called vasopressin ) acts on the kidneys and signals them to retain water, rather than releasing water through the urine. Without ADH, excessive amounts of water can be lost through the urine. This is seen in a condition called central diabetes insipidus .
Oxytocin primarily acts on the uterus to stimulate contractions. It can also act on the breasts to stimulate the secretion of milk.

In the anterior lobe, several different types of hormones are produced:

Growth hormones (GH, also known as somatotropin ) stimulate growth in children and play an important role in regulating the metabolism and processing of proteins, fats, and carbohydrates in the body. Abnormal levels of GH in children can lead to dramatic growth defects including dwarfism (when GH levels are too low) and gigantism (when GH levels are too high). In adults, a small amount of GH is normally produced; however, excess production of GH in adults can lead to excessive growth of bone and tissues, particularly in the face, hands, and feet (a condition known as acromegaly )

Prolactin primarily acts on the breast to stimulate the production of milk. It also plays a role in development of eggs in a woman's ovaries and may help to regulate the immune system.
Adrenocorticotropic hormone (ACTH, also known as corticotropin ) stimulates growth of the adrenal glands, which are located just above the kidneys. ACTH triggers the adrenal glands to produce steroid hormones such as cortisol. Excessive production of steroid hormones by the adrenal glands is called Cushing's disease , and leads to a number of symptoms, including weight gain, increased fat around the neck and back, poor wound healing, high blood pressure, increased blood sugar, excessive hair growth, and erratic mood changes.

Thyroid-stimulating hormone (TSH, also known as thyrotropin ) acts on the thyroid gland to stimulate the production of thyroid hormone. Thyroid hormone is the main regulator of overall metabolism in the body. Too much thyroid hormone (called hyperthyroidism ) can lead to weight loss, irritability, and cardiac arrhythmias. Too little thyroid hormone (called hypothyroidism ) can lead to weight gain, excessive sleepiness, and fatigue.

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) (collectively also known as gonadotropins ) act on the gonads (the testes in men and the ovaries in women). In men, LH causes the testicles to produce testosterone, the primary male hormone, while FSH regulates the production of sperm. In women, LH causes the ovaries to produce estrogen, the primary female hormone, and also plays an important role in stimulating the release of eggs from the ovary. LH has a critical role during pregnancy by regulating hormonal levels so that the pregnancy is maintained. FSH in women primarily acts to regulate the maturation of eggs within the ovary. Decreased levels of FSH and/or LH (known as hypogonadism) can lead to failure of sperm production in men and cessation of the menstrual cycle in women.