Pituitary Gland

Pituitary Gland
Pituitary Gland Anatomy. Stocktrek Images/Getty Image

The pituitary gland is a small endocrine organ that controls a multitude of important functions in the body. It is divided into an anterior lobe, intermediate zone, and posterior lobe, all of which are involved in either hormone production or hormone secretion.  The pituitary gland is termed the "Master Gland" because it directs other organs and endocrine glands to either suppress or induce hormone production.

Hypothalamus-Pituitary Complex

The pituitary gland and hypothalamus are closely connected both structurally and functionally. The hypothalamus is an important brain structure that has both nervous system and endocrine system function. It serves as a link between the two systems translating nervous system messages into endocrine hormones.

The posterior pituitary is composed of axons that extend from the neurons of the hypothalamus. The posterior pituitary also stores hypothalmic hormones. Blood vessel connections between the hypothalamus and anterior pituitary allow hypothalamic hormones to control anterior pituitary hormone production and secretion. The hypothalamus-pituitary complex serves to maintain homeostasis by monitoring and adjusting physiological processes through hormone secretion.

Pituitary Function

The pituitary gland is involved in several functions of the body including:

  • Growth Hormone Production
  • Production of Hormones That Act on Other Endocrine Glands
  • Production of Hormones That Act on the Muscles and the Kidneys
  • Endocrine Function Regulation
  • Storage of Hormones Produced by the Hypothalamus

Location

Directionally, the pituitary gland is located in the middle of the base of the brain, inferior to the hypothalamus.

It is nestled within a depression in the sphenoid bone of the skull called the sella turcica. The  pituitary gland extends from and is connected to the hypothalamus by a stalk-like structure called the infundibulum, or pituitary stalk.

Pituitary Hormones

The posterior pituitary lobe does not produce hormones but stores hormones produced by the hypothalamus. Posterior pituitary hormones include antidiuretic hormone and oxytocin. The anterior pituitary lobe produces six hormones that are either stimulated or inhibited by hypothalamic hormone secretion. The intermediate pituitary zone produces and secretes melanocyte-stimulating hormone.

Anterior Pituitary Hormones

  • Adrenocorticotropin (ACTH): stimulates the adrenal glands to produce the stress hormone cortisol.
  • Growth Hormone: stimulates growth of tissues and bone, as well as the breakdown of fat.
  • Luteinizing Hormone (LH): stimulates male and female gonads to release sex hormones, testosterone in men and estrogens and progesterone in women.
  • Follicle-stimulating Hormone (FSH): promotes the production of male and female gametes (sperm and ova).
  • Prolactin: stimulates breast development and milk production in women.
  • Thyroid-stimulating Hormone (TSH): stimulates the thyroid to produce thyroid hormones.

    Posterior Pituitary Hormones

    • Antidiuretic Hormone (ADH): helps maintain water balance by decreasing water loss in urine.
    • Oxytocin - promotes lactation, maternal behavior, social bonding, and sexual arousal.

    Intermediate Pituitary Hormones

    • Melanocyte-stimulating Hormone (MSH): promotes melanin production in skin cells called melanocytes. This induces skin darkening.

    Pituitary Disorders

    Pituitary disorders result in the disruption of normal pituitary function and the proper functioning of target organs of pituitary hormones. These disorders are most commonly the result of tumors, which cause the pituitary to produce either not enough or too much of a hormone. In hypopituitarism, the pituitary produces low levels of hormones. The insufficiency of pituitary hormone production causes a deficiency in the production of hormones in other glands.

    For example, a deficiency in thyroid-stimulating hormone (TSH) production can result in an underactive thyroid gland. Lack of thyroid hormone production slows down normal body functions. Symptoms that may arise include weight gain, weakness, constipation, and depression. Insufficient levels of adrenocorticotropic hormone (ACTH) production by the pituitary results in underactive adrenal glands. Adrenal gland hormones are important for maintaining vital body functions such as blood pressure control and water balance. This condition is also known as Addisons disease and can be fatal if not treated.

    In hyperpituitarism, the pituitary is overactive producing hormones in excess. An overproduction of growth hormone may result in acromegaly in adults. This condition results in excessive growth of bones and tissues in the hands, feet, and face. In children, overproduction of growth hormone may result in gigantism. Overproduction of ACTH causes the adrenal glands to produce too much cortisol, which results in problems related to metabolism regulation. Overproduction of the pituitary hormone TSH may result in hyperthyroidism, or the overproduction of thyroid hormones. An overactive thyroid produces symptoms such as nervousness, weight loss, irregular heartbeat, and fatigue.