What is the pituitary gland ?
Pituitary gland or the brain appendage is a gland located in the head, under the brains, which secretes many hormones. The pituitary gland plays an important role in the regulation of a large number of hormones. The gland is about the size of a chickpea (diameter approximately one centimeter) and is located in a cavity in the skull base (the so-called Turkish saddle or sella turcica in Latin), behind the nose. In the human body it weighs about 0.5 grams. The pituitary gland secretes hormones that regulate 9 homeostasis. The posterior lobe of the pituitary gland is part of the diencephalon. With the construction in the embryonic stage of the anterior pituitary is formed from a piece of the epithelium monddak; called Rathke's pouch.
The pituitary gland is made up of three parts:
-The anterior lobe (pars anterior or anterior pituitary)
-Lobe (pars posterior or neurohypophysis)
-The intermediate lobe (pars intermedia)
The posterior lobe of the pituitary gland state with long axons directly in connection with the hypothalamus. The anterior lobe of the pituitary gland is via a portal vein system connected to the hypothalamus. This responds to hormones in the blood and sends to the pituitary hormones when there is more or less of a hormone is needed. Through the pituitary stalk is partly dopamine in the pituitary gland correctly that inhibits the release of prolactin.
The anterior lobe (adenohypophysis)
In the anterior pituitary are produced many hormones that affect other endocrine glands. The anterior pituitary produces:
-Growth hormone (GH) or somatotroop hormone (STH) → regulates the growth of long bones (as long as the epiphyseal plates are not yet ossified) and the growth of muscle tissue. Human Growth Hormone also named (HGH).
-Thyreotroof or thyroid-stimulating hormone (TSH) → converts this to the thyroid gland to the production of thyroid hormone thyroxine (= T4) and tri-jew thyronine / triiodothyronine (= T3). It also ensures that there is produced in the thyroid calcitonin. Calcitonin ensures that the calcium content is reduced in the blood. This is done to inhibit, among other things by the calcium in the bones on the store and the resorption of calcium in the kidneys and intestines.
-Adrenocorticotrophic hormone or corticotropin (ACTH) → converts adrenal cortex up to the production of adrenal cortex hormones.
-Gonadotropic hormones (affecting the ovaries and testes). Namely:
*Follicle stimulating hormone (FSH) → promotes the growth and maturation of follicles in the ovaries in women and spermatogenesis in men in the testes
*Luteinizing hormone (LH) or interstitial cells stimulating hormone (ICSH) → the gonadotropic hormones also stimulate the hormone production of the gonads (gonads).
-Prolactin → this is mainly released during pregnancy and lactation.
-Melanocyte-stimulating hormone or melanotropin (MSH) → stimulates the production (melanogenesis), and release of melanin by melanocytes in the skin.
-Endorphins → work primarily pain suppression, but also provide a sense of happiness or euphoria.
The posterior lobe (neurohypophysis)
The posterior pituitary is important for the water and moisture regulation in the body. It is a repository for two hormones produced by the hypothalamus:
-Antidiuretic hormone (ADH) or vasopressin → promotes fluid retention; creates a rising blood pressure and calls on male aggression.
-Oxytocin (OT) → promotes contraction of epithelial and myoepitheelklierweefsel of the breast, which leads to secretion of lactine. It also leads to the contraction of smooth muscle in the uterus (womb).
Variations between vertebrates
All vertebrates have a pituitary gland, but the structure thereof varies between the different groups. In mammals, the pituitary exists only in compact form. Amphibians, reptiles and birds, the pituitary is becoming increasingly better developed. When the agent tetrapods lobe is not well developed and in birds is missing it completely. In fish, the middle lobe, however well developed.
Pituitary gland diseases
The most common disorder of the pituitary gland is a tumor. These growths are usually benign and can be roughly divided into the following types:
-Pituitary enlargement with excessive production of prolactin (prolactinoma)
-Pituitary magnification with excessive production of growth hormone, which leads to acromegaly
-Pituitary magnification with excessive production of ACTH and as a result Cushing's syndrome
-Non-endocrine active tumors.
Here are described a number of disorders of the pituitary gland
-Acromegaly: Acromegaly is caused by a hormone-producing tumor on the pituitary gland, causing too much growth hormone is made. These growths are benign and do not spread through the body. Acromegaly is a very rare condition. In the Netherlands, the diagnosis is made annually by fifty to one hundred patients.
The symptoms are: change of appearance, enlargement of the hands and feet, headache, fatigue, excessive sweating and in some cases decrease of sex positions. By treating these symptoms can be better. Fatigue and sleep disturbances sometimes among the first symptoms. The cause of the enlargement of the hands and feet is an excess of the growth hormone. Because the pituitary gland enlarges, one can get a headache. Also, the pituitary gland to put pressure on the optic nerve, which may result in visual disturbances, and the field of view.
-Craniofaryngeoom: This is a rare, benign tumor on pituitary gland. This tumor manifests itself somewhere between the 5th and 10th year and in early adolescence between the 15th and 18th years. A second peak is manifested in humans around the 55th year of life.
Symptoms: The first symptoms are often headaches and vision problems. When the tumor grows, it creates pressure on the hypothalamus and pituitary. That can result from working properly. This can cause a range of symptoms and signs.
-Diabetes insipidus: Diabetes insipidus is caused by a lack of or insufficient susceptibility to anti-diuretic hormone (ADH), previously called vasopressin.
Symptoms: Many thirsty and urinate a lot of very watery urine. However, the condition is treatable with drugs, in the form of tablets, a nasal spray or injections. The diagnosis is made by blood and urine tests and possibly a water deprivation test.
-Kallmann syndrome: Kallmann syndrome is a congenital condition whose main features: the lack of puberty, underdevelopment of the genitalia and hardly able to smell. Kallmann syndrome is defined as puberty unpaid and lacking the ability to smell. When Kallmann syndrome, there are no connections arise between the pituitary gland and the hypothalamus. As a result, the hypothalamus can not stimulate the pituitary gland to release hormones when puberty should start.
-Prolactinoma: A prolactinoma is a benign tumor on pituitary gland. It causes excessive production of the hormone prolactin, the hormone that normally triggers the milk after childbirth.
In women, symptoms like tepeluitvloed, breast tenderness, decreased sex drive, decreased fertility and lack occurrence of menstruation. In men act almost no noticeable complaints; only disturbed potency and decreased sexual occur regularly.
-Sheehan syndrome: This is a very rare condition. It occurs when the mother during childbirth lose so much blood that the pituitary is in trouble and (partially) dies. This causes problems with the management of the thyroid, adrenals, gonads, and growth hormone. The treatment consists in hormone replacement therapy.
The pituitary gland can also make little hormone; this is called hypopituitarism. The hormonal deficiency can be supplemented with medication. In exceptional cases, one can decide to remove the organ (hypophysectomy).