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The Pituitary Gland

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The word 'pituitary' comes from the Greek word 'pituita'. It is also known as hypophysis or hypophyseal gland. It is also called the 'master gland' as it secretes releasing glands that control the secretions of many endocrine glands.

Origin: It has a dual origin. Adenohypophysis is derived from embryonic ectoderm and neurohypophysis is derived from neural ectoderm.

Location: It is a cranial endocrine gland. It is located at the base of the brain below the hypothalamus. It is attached to the hypothalamus by a pituitary stalk. It is lodged inside a cavity on the sphenoid bone called pituitary fossa or sella turcica.

Structure: It is a small gland about the size of a pea. It weighs about 500 grams and is 1.3cm in diameter. It has three lobes:- an anterior lobe, an intermediate lobe, and a posterior lobe. The anterior and intermediate lobe constitute the adenohypophysis and the posterior lobe constitutes the neurohypophysis.

Function: The hormones secreted by adenohypophysis are as follows.

i)Thyrotropin/Thyroid-stimulating hormone(TSH): It stimulates the thyroid gland to produce tetra-iodothyronine(T4) and tri-iodothyronine(T3).

ii)Adrenocorticotropic hormone(ACTH): It stimulates the adrenal gland to produce adrenocorticosteroids:- mineralocorticoids, glucocorticoids and gonadocorticoids.

iii)Growth hormone(GH): It stimulates the growth of tissues of the body.

iv)Prolactin(PRL): It stimulates the mammary glands to produce milk after birth.

v)Gonadotropins: Follicle-stimulating hormone(FSH) and luteinizing hormone(LH) are gonadotropins.

The hormones produced by neurohypophysis are as follows.

i)Oxytocin: It causes the contraction of the myoepithelium of mammary glands and myometrium of the uterus during childbirth.

ii)Vasopressin/Anti-Diuretic Hormone(ADH): It prevents diuresis(excess urination) by stimulating distal convoluted tubule(DCT) and collecting duct(CD).

The disorders related to secretions of the pituitary gland are as follows.

i)Dwarfism: It is caused to the deficiency of growth hormone in early childhood. It is characterized by small height.

ii)Gigantism: It is caused by hypersecretion of growth hormone before puberty. It is caused by extraordinary growth in height.

iii)Acromegaly: It is caused due to hypersecretion of growth hormone after puberty. It is characterized by the thickening of bones.

iv)Simmond's disease: It is caused due to deficiency of growth hormones in adults. It is characterized by deterioration of body tissues and aging.