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Hannah Holmes

BIOCHEM 3H03March 5 2014Lecture 19 Hypothalamus and the Pituitary Part IIGROWTH HORMONE DISORDERSExcellent example to look at extremes illustration becomes very definite o Have an overall picture of what GH is doing it affects a number of things o Excess GH for any reason will touch on soonthink about what the processes are in terms of a child and in terms of an adult and how either would be affected by excess GH o Gigantismchildren Unchecked GH in children bones arent fused continualexcessive growth has its own inherent problemsAlso affects everything elseMetabolic effects Glucose metabolism on long term There are a number of effects o AcromegalyadultsUnchecked GH in adults basically same phenomenon excess GH difference is that bones have fuseddevelopmental stages are overStill have unchecked GHSame scenario just different with how its defined with respect to ageCauses of increased GH o Pituitary exGHsecreting tumours o Hypothalamic or ectopic site other than tissue of origin GHRHsecreting tumoursIn level of hypothalamus unchecked secretion of GHRH feedback mechanisms dont work in the case of hormonesecreting tumours doesnt matter if GH and IGF1 are elevated and theyre feeding back like crazy because of the constant GHRH stimulation of the pituitary o Ectopic GHsecreting tumourIn various cancers cells can differentiate in different ways because they all carry the genetic blueprint can secrete whatever it wants to ExCan have a lung thymus or anything secreting excess amounts of GHRHReceptors on pituitary for GHRH just recognize it and get stimulatedas long as it has the right structure it doesnt matter where its from iethe hypothalamus or another tissueCan be active tumours or ectopic tumours secreting GHRH o Or just excessive GH secretionThese disorders are very very rare o For the most part they are also treatable if they are detected early enoughGROWTH HORMONE DISORDERSExcess Growth HormoneGH plays a role in growth and development from 8 months onBefore pubertyexcess GHtall stature gigantismAfter pubertyexcess GHgrowth plates fused so no increase in stature acromegaly o Reach adulthood bones fuse so no more growth in terms of stature but youre still getting the same excessive stimulation hence other tissues grow o Excess soft tissue growth bones and muscles cant really grow anymore so other tissues grow disproportionatelyCoarsening of facial features bone and cartilageThickening up bones plates are fused so theres nowhere for anything to goHyperinsulinemia o GH and insulin are having opposite effects Excess GH secretion mobilizes more FFAs trying to keep blood glucose levels high while insulin keeps trying to tell the body that it doesnt need itAll this physical presentation o Bones are till o Have to start putting it together GH and insulin have opposing effectsCardiac hypertrophy
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