The Pituitary Gland

The pituitary gland, also called the "master gland” of the endocrine system, controls most of the functions of other endocrine glands. It is about the size of a pea, and located in the base of the brain, just behind the bridge of the nose. Attached to the hypothalamus by nerve fibers, the pituitary establishes an important link between the nervous system and the endocrine system. The pituitary gland has two distinct parts, the anterior and the posterior lobes, each of which releases different hormones which affect bone growth and regulate activity in other glands. This master gland releases many hormones which affect growth, sexual development, metabolism and the system of reproduction. The anterior lobe produces thyroid stimulating hormone (TSH), growth hormone, adrenocorticotropic hormone (ACTH), luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin (PRL). Thyroid stimulating hormone stimulates the thyroid gland to produce and secrete thyroid hormone which controls and regulates the basal metabolic rate and plays an important role in growth and maturation. Almost every organ in the body is affected by thyroid hormone. Growth hormone regulates the growth and metabolism of the human system, and the adrenocorticotropic hormone triggers the production and release the hormone cortisol, by the adrenals. Cortisol regulates carbohydrate, fat, and protein metabolism as well as blood pressure. The adrenal glands which sit above the kidneys produce hormones which are also responsible for the body's fight or flight response mechanisms. Luteinizing hormone and follicle stimulating hormone stimulate the ovaries and testes to synthesize and release sex hormones including estrogen and testosterone. These hormones are in charge of sperm and egg maturation and release, while prolactin stimulates the production of milk during breast feeding. The posterior lobe of the pituitary gland produces antidiuretic hormone (ADH) and oxytocin. Antidiuretic hormone, also referred to as vasopressin, increases absorption of water into the blood by the kidneys and therefore decreases urine production. Oxytocin stimulates contractions of the uterus during childbirth and the ejection of milk during breast-feeding. The pituitary can produce either too much or too little of these hormones. Consequently, an imbalance could occur which could lead to disorders of the endocrine system. Hormonal imbalances and deficiencies have several health implications. For example, deficiencies of thyroid hormone, adrenal cortical hormone (cortisol) or antidiuretic hormone (vasopressin) can be life-threatening. Abnormalities of the other hormones, can lead to ill-health and diseases and quality of life can significantly be compromised. Abnormal growth of pituitary cells, including tumors, infections, inflammations, and injuries to the head and brain, can cause the pituitary gland to malfunction. A tumor can make the pituitary to be nonfunctional or function abnormally and prevent it from secreting certain necessary hormones or secrete excessive or very low levels of a very important hormone. For example, high prolactin levels may suppress production of the pituitary hormones, luteinizing hormone and follicle stimulating hormone that stimulate production of estrogen or testosterone, causing infertility, decreased libido, and osteoporosis. Abnormal levels of growth hormone, ACTH, and TSH may cause acromegaly, Cushing's Disease, and hypothyroidism, respectively. Men with pituitary tumors have low testosterone levels and may lose their sex drive and their masculine characteristics, such as hair, muscle, erections, and ability to produce sperm, and eventually self-esteem. On the other hand, women with prolactin producing tumors have low levels of estrogen, and often cease to ovulate during menstrual periods. Females with low sex hormones often develop osteoporosis.