The pituitary is a small gland hung to the floor of the third ventricle by a narrow stalk, the pituitary stalk, and housed in the sella dug the body of the sphenoid. Its weight is 0.60 g, the size of a pea.
It consists of three parts, whose functions are totally different: the anterior lobe, intermediate lobe and the posterior lobe.

The Pituitary

The Anterior Lobe
The anterior pituitary or adenohypophysis is composed of two kinds of cells: cells chromophil rich granules or acidophilic (40% of anterior pituitary cells) or basophils (10% of cells) and cells chromophobe (50% cells) devoid of granules.
The anterior pituitary secretes many susbtances, hormones or stimulines true:

Growth hormone GH (Grow Hormone)
It is also known as growth hormone. It ensures a harmonious development of the human body and is responsible for the size of the subject. It stimulates growth and therefore in this specific action on the growth plates that hypertrophy significantly under its action. The hypophysectomy leads to arrest of growth in young animals, administration of excessive growth hormone to a normal growth track leads to gigantism.

Growth hormone also has a role in healing.
Finally she has metabolic functions:
* on proteins: it has an anabolic action and synthesis of proteins;
* on carbohydrates: it hyperglycaemic action because it mobilizes the sugar by causing the secretion of pancreatic gIucagon;
* on lipids: it mobilizes fat stores and promote their use for the synthesis of proteins.

The anterior pituitary stimulines
The stimulines are hormones, but that target endocrine cell: they are a sort of intermediary, messenger. They are:
* The cortico-Stimuline ACTH: it stimulates areas fasciculata and reticularis of the adrenal glands and hormone production in these areas (cortisol and androgens), however, there is no action of ACTH on the secretion of ‘aldosterone. ACTH stimulates all stages of the formation of steroids from cholesterol.
* The thyrotropin or thyroid stimulating hormone or TSH: it increases the weight and vascularity of the thyroid gland, it stimulates the follicular cells and all stages of the synthesis of thyroid hormones with increased release of these.
* The GnRH:
* FSH: the female, FSH causes follicle maturation but can trigger ovulation (which requires LH) in males, FSH stimulates spermatogenesis;
* LH: in females, it causes, in synergy with FSH, ovulation, corpus luteum formation and secretion of estrogen and progesterone; males, it stimulates the functioning of Leydig cells and production male hormone, it is noteworthy that the GnRH are identical in both sexes, and that their action is different in men and in women;
* prolactin: it has a dual action on the mammary glands. It has a mammotrope (growth of mammary glands in synergy with estrogen, progesterone 1a and S. T. H.) and an effect lactogen (lactogenesis and maintenance of lactation after childbirth).
* The existence of stimulines explains the atrophy of endocrine glands found in the syndrome of hypopituitarism and after hypophysectomy.


The posterior pituitary (or posterior lobe)
The posterior lobe or posterior pituitary gland is made up of special cells, the pituicytes, surrounded by glia cells.
The post-pituitary hormones are actually synthesized in the hypothalamus and the posterior lobe of the pituitary gland is a single storage location from which they are released into the circulation.
These hormones are two in number: vasopressin (antidiuretic hormone) and oxytocin.

Vasopressin (ADH)
It has two actions:
it causes vasoconstriction;
she has an antidiuretic action: it regulates the renal reabsorption of water it tends to increase, by action at the distal tubule and collecting duct of Bellini It also tends to increase the urinary excretion of chlorine and sodium. Its secretion is dependent upon the osmotic pressure of arterial blood, therefore the water content and electrolytes in it. any increase in osmotic pressure causes the secretion of the hormone and, conversely, any decrease in osmotic pressure inhibiting the secretion of vasopressin. Similarly, any decrease in the circulating blood volume (hypovolemia from dehydration or bleeding) triggers, through reflex from volorécepteurs the atrium, a secretion of ADH alteration of post-pituitary and especially of hypothalamus causes diabetes insipidus, a disease characterized by considerable daily diuresis.
Alcohol, cold inhibit the secretion of ADH.

Oxytocin
It causes contraction of smooth muscle cells including those of the uterus: as such it plays a fundamental role in childbirth. It also occurs in association with the prolactin in the onset of lactation. A synthetic oxytocin used in obstetrics, especially in the post partum, the Syntocinon.

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