The pituitary gland is a small endocrine organ that controls a multitude of important functions in the body.
It is divided into the anterior lobe, intermediate zone, and posterior lobe, all of which are involved in hormone production or hormone secretion .
The pituitary gland is called the “master gland” because it directs other organs and endocrine glands to suppress or induce hormone production.
The pituitary gland and the hypothalamus are closely connected both structurally and functionally. The hypothalamus is an important brain structure that has both the nervous system and the endocrine system function.
It serves as a link between the two systems that translate messages from the nervous system into endocrine hormones.
The posterior pituitary is made up of axons that extend from neurons in the hypothalamus. The posterior pituitary also stores hypothalamic hormones.
The blood vessel connections between the hypothalamus and the anterior pituitary allow hypothalamic hormones to control the production and secretion of the anterior pituitary hormone.
The hypothalamic-pituitary complex serves to maintain homeostasis by monitoring and adjusting physiological processes through the secretion of hormones.
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 kidneys.
- Regulation of endocrine function.
- Storage of hormones produced by the hypothalamus.
Directionally, the pituitary gland is located in the middle of the base of the brain, inferior to the hypothalamus.
It lies 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 stem-like structure called the infundibulum, or pituitary stalk.
The posterior pituitary lobe does not produce hormones, but instead stores hormones produced by the hypothalamus. The posterior pituitary hormones include antidiuretic hormone and oxytocin.
The anterior pituitary lobe produces six hormones that are either stimulated or inhibited by the secretion of the hypothalamic hormone. The intermediate zone of the pituitary gland produces and secretes the melanocyte-stimulating hormone.
Anterior pituitary hormones
- Adrenocorticotropin (ACTH): stimulates the adrenal glands to produce the stress hormone cortisol.
- Growth hormone: stimulates the growth of tissues and bones, as well as the breakdown of fat.
- Luteinizing Hormone (LH): stimulates the 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 eggs).
- 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 reducing water loss in the urine.
- Oxytocin: promotes lactation, maternal behavior, social ties and sexual arousal.
Intermediate pituitary hormones
- Melanocyte Stimulating Hormone (MSH): Promotes the production of melanin in skin cells called melanocytes. This induces darkening of the skin.
Pituitary disorders cause the alteration of normal pituitary function and the proper functioning of the target organs of pituitary hormones. These disorders are most commonly the result of tumors, which cause the pituitary gland to make too little or too little of a hormone.
In hypopituitarism, the pituitary gland produces low levels of hormones. Insufficient production of pituitary hormones causes a deficiency in the production of hormones in other glands.
For example, a deficiency in the production of thyroid stimulating hormone (TSH) can result in an underactive thyroid gland. Lack of thyroid hormone production slows down normal bodily functions.
Symptoms that can arise include:
- Weight gain.
- Soft spot.
- Depression .
Insufficient levels of adrenocorticotropic hormone (ACTH) production by the pituitary gland produce underactive adrenal glands.
Hormones from the adrenal glands are important for maintaining vital body functions, such as blood pressure control and fluid balance. This condition is also known as Addison’s disease, and it can be fatal if left untreated.
In hyperpituitarism, the pituitary is overactive, producing excess hormones. An overproduction of growth hormone can cause acromegaly in adults.
This condition causes an overgrowth of bones and tissues in the hands, feet, and face. In children, overproduction of growth hormone can cause gigantism.
The overproduction of ACTH causes the adrenal glands to produce too much cortisol, which causes problems related to the regulation of metabolism.
Overproduction of the pituitary hormone TSH can lead to hyperthyroidism or overproduction of thyroid hormones. An overactive thyroid produces symptoms such as nervousness, weight loss, irregular heartbeat, and fatigue.