Pituitary Gland

The pituitary also referred to, as the “master gland of the body” is a double lobed endocrine gland. The pituitary gland secretes several hormones, which regulate bodily processes, including growth, reproduction and numerous metabolic activities. It is located in a cavity of the sphenoid bone, below the hypothalamus, at the base of the brain. The lobes of the pituitary are as distinct in function as they are in position and tissue type. The posterior lobe is made up of an out growth of neural tissue from the hypothalamus and is responsible for the release of oxytocin and vasopressin. The anterior lobe, which sits towards the front of the head, is a non-neural tissue responsible for the release of eight hormones. The follicle-stimulating hormone (FSH), luteinizing hormone (LH), growth hormone (GH), thyroid-stimulating hormone (TSH), prolactin, adrenocorticotropic hormone (ACTH), beta-lipotropin and beta-endorphin are all secreted by the anterior pituitary. Hypophysiotropic hormones of the hypothalamus stimulate the majority of the hormones produced by the anterior pituitary.

To demonstrate how an endocrine gland might function, we will focus on the non steroid growth hormone (GH) and its pathway. The hypothalamus, upon stimulus by factors such as stress, nutrient levels, exercise, sleep, and neurotransmitters, produces a hypophysiotropic hormone called growth hormone-releasing hormone (GHRH) which stimulates the release of GH from the anterior pituitary by means of as series of capillaries and portal vessels. The growth hormone will then be released back into the capillaries and travel to the target cells, in this case the liver, although GH acts on various other cells. Upon arrival, GH works indirectly on the target cells by producing a mitogen specified as insulin-like growth factor I (IGF-I), also known as somatomedian C. IGF-I is secreted by the liver, enters the blood stream and functions as a hormone. IGF-I is necessary for normal fetal growth, especially affecting the development of the nervous system. Negative feedback controls for the growth hormone inhibiting or stimulating further GH release from the anterior pituitary. A variety other hormones, namely the thyroid, sex and insulin hormones also help to regulate GH.