Pituitary Hormones

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Growth Hormone (Somatotropin) Naturally occuring protein hormone Regulates body growth Effects of GH Direct Reduced glucose transport and metabolism Increased lipolysis Increased amino acid transport Increased protein synthesis Increased IGF-I production Increased fibroblast differentiation Indirect Promotion of growth and endocrine effects Reduction in insulin receptors in liver Localized decrease in adipose tissue free fatty acides released Increases in both transcription and translation Chondrocyte, osteoblast, and adipocyte formation Muscle Growth increased rates of muscle protein synthesis decreased protein degradaion increased RNA and DNA often accompanying increased protein accretion increased DNA is likely a result of increased satellite cell activity Bone Growth mediated through IGF-I IGF-I increases chrondrocyte proliferation increases osteoblast activity GH leads to increased bone length prior to epipyseal closure GH increases periosteal growth contribuing to increased bone mass Regulation of Growth Hormone Secretion Events increasing rate of release Starvation Hypoglycemia Acute hypoglycemia: potent stimulator of GH release Low FA in blood Severe chronic protein deprivation high circulating GH levels Stress Excitement Trauma Exercise Amino Acid Supplementation Arginine, Orthanine PreREM Sleep Hypothlamus Growth hormone releasing hormone Somatostatin / growth hormone inhibitory hormone Neurotransmitters increasing GH release Catecholamines Domamine Serotonin Metabolic effects Increased lipolysis Increased protein synthisis GH affect on muscle is mediated through IGF-I and binding sites for IGF-I Decreased glucose use Interacts with receptors on cell membrane Liver, kidney, muscle Causes release of IGF-I into circulation inturn activates target tissue various binding proteins are involved in transporting IGF-I to target tissue Growth hormone is species specific IGF-I can stimulate proliferation and differentiation of myoblasts increases uptake of glucose and amino acides into muscle negative feedback on pituitary increases release of somatostatin TSH Stimulates Thyroid FSH, LH FSH: Folical Stimulationg Hormone LH: Luteinizing hormone Control overies, estrogens, and progesterone Prolactin Regulates milk production Oxytocin Milk release ACTH Stimulates adrenal production of Cortisol ADH Fluid balance