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Growth hormone Prof/ Faten & Dr/Tag

Growth hormone Prof/ Faten & Dr/Tag. Growth Hormone (hGH) . Somatotropin. Small protein expressed from anterior lobe of pituitary produced by Somatotroph cells of the anterior pituitary Growth hormone (hGH) is a peptide hormone Essential for normal development

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Growth hormone Prof/ Faten & Dr/Tag

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  1. Growth hormoneProf/Faten & Dr/Tag

  2. Growth Hormone (hGH) . Somatotropin Small protein expressed from anterior lobe of pituitary produced by Somatotroph cells of the anterior pituitary Growth hormone (hGH) is a peptide hormone Essential for normal development Promotes growth, especially in children and at puberty

  3. INDIRECT ACTIONS OF hGH • The effect of hGH on the liver is to produce a number of Somatomedins or growth factors now usually called Insulin-like Growth Factors – IGFs. • The actions of hGH are mediated mainly through IGF-1, the effects of which are to stimulate growth in bone, protein synthesis in muscle and lipolysis of fat.

  4. Somatic growth • hGH stimulates linear bone growth primarily by increasing amino acid uptake and protein synthesis in (bone cells). • It acts indirectly through stimulating the synthesis of somatomedins (insulin-like growth factors (IGF)by the liver • cause secretion of collagen and minerals necessary for cartilage and bone growth. • hGH causes an increase in organ size and function. It promotes both increased sizes of cells and increased mitosis, with development of increased numbers of cells.

  5. Non-Growth Actions of hGH • hGH also has direct actions on fat cells, liver and muscles which are not growth promoting but are metabolic in function. • It causes the breakdown of fat • - Increased rate of protein synthesis in all cells of the body t • stimulates glucose produced by gluconeogenesis bringing about a rise in plasma glucose. • -

  6. Effect MetabolismEffect on CHO and fat metabolism(Diabetogenic) • The effect of hGH on metabolism is to increase the energy substrates, glucose and free fatty acids, The effect of hGH on increasing serum glucose levels is two-fold • glucose uptake by muscle and adipocytes is decreased. • glucose synthesis (gluconeogenesis) by the liver is stimulated.

  7. Effect Metabolism (cont..) Effect on Fat MetabolismCauses Insulin Resistance • hGH decreases body fat by increasing lipolysis in adipose tissue leading to decreased fat storage and increased FFA concentration in circulation i.e. it causes mobilization of fats. • The result is decreased fat storage • - High blood glucose& fatty acids causes Insulin Resistance

  8. Effect on protein and electrolyte metabolism(Protein Sparing) • Growth hormone is a protein anabolic hormone • Increase in lean body mass and a decrease in body fat along with an increase in metabolic rate and in serum cholesterol

  9. Effect on Tissues • The mediators of hGH action are called insulin-like growth factors (IGF) or Somatomedins which are produced by the liver • In addition, hGH increases lean body mass through the increase of muscle protein synthesis. • -Size of internal organs also increased • Following puberty, hGH levels decline during adulthood and decrease further with aging.

  10. Hypothalamus –Ant: Pituitary • The synthesis and release of GH is under the control of the hypothalamic hormones. • The hypothalamus produces a pair of hormones, growth hormone releasing hormone (GHRH) and • Growth hormone inhibitory hormone (GHIH or Somatostatin). • Both act on the anterior pituitary to stimulate or inhibit the production of growth hormone.

  11. CONTROL OF GROWTH HORMONE SECRETION = Somatostatin (GHIH) = Somatomedin-C

  12. Regulation of release of growthhormone • The regulation of the ‘HYPOTHALAMIC –PITUITARY axis’ is by IGF-1, which acts on the hypothalamus to inhibit GHRH and stimulate Somatostatin or (GHIH). • Circulates in the blood tightly bound to a large plasma protein. • Has a long half-life. • The levels of hGH rise during sleep, in adults as well as children.

  13. Excess and deficiency of HGHExcess HGH • The most common cause of excess is a pituitary tumor. • In children who are still growing, excess hGH causes Gigantism. • In adults whose long bones can no longer be extended, the condition is known as Acromegaly.

  14. Giagantism Due to tumour in the cells secreting growth hormone in the anterior pituitary. -Increased secretion of growth hormone before adolescence (before union of the ends of the bones with the shafts (bone maturation). -The giant becomes longer than usual) more than 2 meters length -Muscles may be well developed but later undergo some atrophy and weakening. -The life span is shorter than normal

  15. Acromegaly • An excessive production of growth hormone in an adult results in enlargement of skeletal extremities. • For instance, the flat bones and soft tissues of the hands, feet, face,nose (acromegalic facies) and lower jaw (prognathism) and forehead become enlarged and the skin becomes coarse. • Growth hormone can also stimulate the growth of connective tissue such as ligaments, capsules and synovial membranes. • Another condition commonly associated with Acromegaly is diabetes mellitus. As growth hormone causes tissue resistance to insulin and is therefore Diabetogenic. • - • -liver, kidney, spleen becomes larger than normal

  16. Growth hormone deficiency (Dwarfism) • the child becomes shorter than normal • -Occurs when growth hormone decreases • or become absent in childhood and • before adolescence • In adults a growth hormone deficiency is not a major problem and is very treatable

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