Adenohypophysis

Adenohypophysis

1. ADENOHYPOPHYSIS M.Rajkumar.M.sc,M.Phil

2. Adenohypophysis , the anterior portion of the pituitary gland, divided into two parts – the pars anterior and the pars intermermeda – The pars anterior forms the major portion of the adenohyphysis and is divided from the tiny pars intermedia by a narrow left and some connective tissue. Somatotrophs – secrete growth hormone (GH) Corticotrophs – Secrete adrenocortiocotropic hormone (ACTH) Thyrotrophs – secrete thyroid-stimulating hormone (TSH) Lactotrophs – secrete prolactin (PRL) Gonadotrophs – secrete luteinizing hormone (LH) and follicle – stimulating hormone (FSH) ADENOHYPOPHYSIS

3. GROWTH HORMONE Growth hormone (GH), or sometotropin (STH), is thought to promote bodily growth indirectly by stimulating the liver to produce certain growth factors, which, in turn, accelerate amino acid transport into cells. Rapid entrance of amino acids from the blood into the cells allows protein anbolism within the cells to accelerate. Increased protein anabolism allows an increased rate of growth. GH promotes the growth of bone, muscle, and other tissues.

4. Hypersecretion of GH during the growth years (before ossification of the epiphyseal plates) causes an abnormally rapid rate of skeletal growth. This condition is known as gigantism (see figure, left). Hypersecretion after skeletal fusion has occurred can result in acromegaly , a condition in which cartilage still left in the skeleton continues to form new bone. HYPERSECRETION

5. Hyposecretion of GH during growth years may result in studend body growth, known as pituitary dwarfism. For merly , patients were treated only with GH extracted from human tissues.

6. GH affects metabolism in these ways: Promotes protein anabolism (growth, tissue repair) Promotes lipid mobilization and catabolism Indirectly inhibits glucose metabolism Indirectly increases blood glucose Levels

7. Prolactin (PRL), produced by acidophils in the pars anterior, is also called lactogenic hormone. Both names of this hormone suggest its function in “generating” or initiating milk secretion (lactation). During pregnancy, a high level of PRL promotes the development of the breasts in anticipation of milk secretion birth of an infant, PRL in the mother simulates the glands to begin milk secretion. Hypersecretion of PRL may cause lactation in normal women, disruption of the menstrual cycle, and impotely men. Hyposecretion of PRL is usually insignificant exe women who want to nurse their children. Milk production not be initiated or maintained without PRL. PROLACTIN

8. Tropic hormones are hormones that have a simulating other endocrin gland. These hormones stimulate the ment of their target glands and tend to stimulate synthesis creation of the target hormone . Four principal hormones are produced and secreted by the basophils of the anterior. Thyroid-stimulating hormone (TSH) or thyrotrophic motes and maintains the growth and development target gland-the thyroid. TSH also causes the gland to secrete its hormones. TROPIC HORMONE

9. A hormone (ACTH), or adrmcotropin , promotes and maintains normal growth development of the cortex of the adrenal gland. ACTH also stimulates the adrenal cortex to synthesize and secrete some of its hormones. ADRENOCORTICOTROPIC HORMONE

10. HYPERSECRETION OF TROPIC HORMONE secretion of the tropic hormones may result form a pituitary induce the tropic hormones produced at higher than level cause hypersecretion in their target gland. This may result in effects throughout the body. HYPOSECRETION OF TROPIC HORMONE Hyposecretion of tropic hormones often causes their target glands to secrete less than a normal amount of their hormones may disrupt reproduction , kidney function , overall metabolism and other processes.

11. Control of secretion in the adenohypophysis Cell bodies of neurons in certain parts of the hypothalamus Chemical that their axons secrete into the blood. chemicals, generally called releasing hormones, travel through a complex of small blood vesels called the hypophyseal system. CONTROL OF SECRETION IN ADENOHYPOPHYSIS

12. Growth hormone – releasing hormone (GHRH) Growth hormone – inhibiting hormone (GHIH) (also called somatostatin (SS) Corticotropin-relasing hormone (CRH) Thyrotropin-relasing hormone (TRH) Gonadotropin -releasing hormone ( GnRH ) Prolactin-relesing hormone (PRH) Prolactin -inhibiting hormone (PIH) The following is a list of some of the important hormones secreted by the hypothalamus in to hypophyseal portal system .

13. Clinical facts furnish interesting evidence about feedback control of hormone secretion by the anterior pituitary gland and its target glands. For instance, patients who have the pituitary gland removed ( Hypophysectomy ) surgically or by radiation must be given hormone replacement therapy for the rest of their lives. If not they will develop thyroid, adrenal cortical, and gonadotropic deficiencies-deficiencies of the anterior pituitary’s target gland hormones. CLINIC AL EVIDENCE OF FEEDBACK CONTROL

14. Therefore both psychosomatic (mind influencing the body) and somatopsychic (body influencing the mind) relationship exist between human body systems and the brain Hypothalamus FSH & LH GH Anterior Pituitary GHIH/SS GHRH GnRH TRH PRIH PRH CRH TSH Prolactin ACTH + - - + + + - + +

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