Maintaining proper functioning of the body throughout any of a number of different physiologic events requires constant fine tuning. The body relies on the action of what is known as the endocrine system and its many different hormones to regulate these functions. The pituitary gland (also known as the hypophysis) plays a central role in many of these events producing a wider array of hormones than any other gland in the body.
Structure of the Pituitary Gland
The pituitary gland is a little bigger than a pea and is nestled in a bony depression, known as the sella turcica, below the underside of the brain. Attached to a stalk known as the infundibulum, which extends down from the hypothalamus of the brain, the pituitary gland is divided into two major lobes, the anterior lobe (or adenohypophysis) and the posterior lobe (or neurohypophysis). [There is an intermediate lobe in the pituitary gland in other species but it is rather rudimentary in humans.] The pituitary stalk that attaches the gland to the infundibulum is connected to the posterior lobe.
What Hormones Are Produced by the Pituitary
The different lobes of the pituitary gland produce entirely different hormones. The hormones have an impact on all of the other glands in the body.
Posterior pituitary hormones:
- Oxytocin
- Anti-diuretic hormone
Anterior pituitary hormones
- Growth hormone
- Luteinizing hormone
- Adrenocorticotrophic hormone
- Prolactin
- Follicle stimulating hormone
- Thyroid stimulating hormone
These hormones can regulate growth, milk production by the breast, uterine contractions during birthing, water retention or removal by the kidneys, egg production by the ovaries, stress hormone production by the adrenal glands, and the activity of the thyroid gland.
How the Pituitary Gland Is Controlled
The two lobes of the pituitary gland are largely regulated by different systems. The cells of the posterior lobe of the pituitary receive connections from the axons of neurons that are located in the hypothalamus of the brain. These neurons directly signal to the posterior lobe cells to release their hormones. In contrast, the anterior lobe of the pituitary receives signals, also from the hypothalamus, but by entirely different means. Cells in the hypothalamus release regulatory molecules into the blood in a specialized series of blood vessels that then transit directly to the anterior lobe. Through this so-called “portal” blood vessel system, the hypothalamus can release hormones that signal the cells of the anterior pituitary to either start releasing or stop releasing its hormones. Some of these regulatory hormones made in the hypothalamus include corticotrophin releasing hormone (CRH) and gonadotropin releasing hormone (GnRH).
The different hormones that are produced in the pituitary gland are synthesized in specific, specialized cells. For instance, growth hormone is produced in the anterior lobe by cells known as somatotrophs, while thyroid stimulating hormone is made in the thyrotrophs. This specialization is, in part, responsible for the different syndromes and diseases that are associated with dysfunction of specific cell types in the pituitary gland such as acromegaly and Cushing’s disease.
For more information about the pituitary gland visit the Pituitary Society website.
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