GROWTH HORMONE D. C. MIKULECKY PROFESSOR OF PHYSIOLOGY AND FACULTY MENTORING PROGRAM

GROWTH zMOST RAPID DURING PRENATAL PERIOD zJUVENILE PERIOD: GH IS VERY IMPORTANT, BUT ALSO INSULIN AND THYROID HOMONE zADOLESCENT: ANDROGENS AND ESTROGENS AS WELL-SPEED UP GROWTH AND BRING BONE GROWTH TO A HALT

CONTROL OF GROWTH zGENETIC POTENTIAL zDIET zDISEASE zHORMONES

ANTERIOR PITUITARY HORMONES: GROWTH HORMONE (SOMATOTROPIN) zLIVER zSOMATOMEDINS zBONE zSOFT TISSUE zGROWTH(ABOUT 30% OF THE GENETIC POTENTIAL) z MANY TISSUES z INTERMEDIARY METABOLISM z INCREASE OR DECREASE

GROWTH HORMONE: SYNTHESIS, SECRETION, AND METABOLISM zABOUT 1/6 OF THE AP CELLS z MG STORED z10X ANY OTHER PITUITARY HORMONE zTWO FORMS 22K AND 20K zBOUND TO PROTEIN IN BLOOD (SAME COMPOSITION AS RECEPTOR) zCANNOT ENTER CELL zDEGRADED IN TARGET CELLS AFTER UPTAKE BY RECEPTOR MEDIATED PROCESS

METABOLIC ACTIONS OF GROWTH HORMONE zDECREASES SENSITIVITY OF MUSCLE AND FAT CELLS TO INSULIN zSENSITIZES BETA CELLS TO SIGNALS FOR INSULIN SECRETION (GET PROTEIN SYNTHESIS WITHOUTDECREASE IN BLOOD GLUCOSE) zMOBILIZES TRIGLYCERIDE FAT STORED IN ADIPOSE TISSUE zCONSERVES GLUCOSE FOR BRAIN zDIABETOGENIC EFFECT

GH AND AGE zSECRETED THROUGHOUT LIFE zRATE DECREASES FROM zMAY ACCOUNT FOR LOSS OF BODY MASS IN THE ELDERLY zCHANGES OCCUR IN BOTH FREQUENCY AND MAGNITUDE OF SECRETIONS

GROWTH PROMOTING ACTIONS OF GROWTH HORMONE zSOFT TISSUES: STIMULATES CELL DIVISION, INCREASES SIZE OF CELLS zSTIMULATES ALMOST ALL ASPECTS OF PROTEIN SYNTHESIS zINHIBITS PROTEIN DEGRADATION zPROMOTES UPTAKE OF AMINO ACIDS

GROWTH PROMOTING ACTIONS OF GROWTH HORMONE zBONE: PROMOTES GROWTH OF LONG BONES zTHICKNESS zLENGTH zAT END OF ADOLESCENCE, SEX HORMONES STOP THIS ACTION

GROWTH HORMONE ACTS THROUGH SOMATOMEDINS zPEPTIDE MEDIATORS: SOMATOMEDINS zCLOSELY RELATED TO INSULIN-LIKE GROWTH FACTORS IGF-I AND IGF-II zPRODUCED IN LIVER AND OTHER TISSUES zALSO PARACRINE EFFECTS

REGULATION OF GROWTH HORMONE SECRETION HIGHER BRAIN CENTERS (+) (-) HYPOTHALAMUS GH-RHSST PITUITARY TARGET CELLS GH SOMATOMEDINS

GHRH AND GHIH zANTAGONIST IN CONTROL OF GROWTH HORMONE SECRETION zNEGATIVE FEEDBACK zDIURNAL RHYTHM: GH SECRETED AT NIGHT zEXERCISE, STRESS, HYPOGLYCEMIA

ABNORMAL GH SECRETION zDEFICIENCY: DWARFISM, REDUCED MUSCLE STRENGTH, DECREASED BONE DENSITY zEXCESS:GIGANTISM, ACROMEGLY

EPINEPHRINE, CORTISOL, AND GROWTH HORMONE zALL INCREASE BLOOD GLUCOSE AND FATTY ACIDS zCORTISOL INCREASES BLOOD AA AND DECREASES MUSCLE PROTEIN zGH DECREASES BLOOD AA AND INCREASES MUSCLE PROTEIN

EFFECTS OF GROWTH HORMONE ON BODY COMPOSITION zDEFICIENCY PROMOTES HIGHER PERCENTAGE OF FAT zPROMOTES GROWTH OF MUSCLE, SKIN, HEART, AND MOST INTERNAL ORGANS EXCEPT LIVER, SPLEEN, THYROID, GONADS, OR REPRODUCTIVE ORGANS.

SYNERGISM OF GH WITH OTHER HORMONES zTHYROID zINSULIN zGONADAL HORMONES zGLUCOCORTICOIDS zOTHER HORMONES AND GROWTH FACTORS

THYROID AND GROWTH zGROWTH STUNTED IN ABSENCE zEXCESS MAY STIMULATE RATE BUT NOT DRAMATICALLY zPROMOTE GH SYNTHESIS zPERMISSIVE EFFECT ON GH AT TARGETS

INSULIN zIMPORTANT DURING FETAL PERIOD IN CONTRAST TO GH AND THYROXINE zCHILDREN OF DIABETIC MOTHERS CAN BE LARGER zRELATED STRUCTURALLY TO THE SOMATOMEDINS zWITHOUT INSULIN, NORMAL RESPONSES TO GH ARE NOT SEEN zREGULATOR OF PROTEIN SYSNTHESIS? zREGULATOR OF ENERGY METABOLISM

GONADAL HORMONES: ANDROGENS zLINEAR GROWTH BEFORE EPIPHYSIS FUSES zENHANCED GH SECRETION zGROWTH OF MUSCLE: DOUBLING OF MUSCLE MASS IN BOYS AT PUBERTY (SIZE AND NUMBER OF MUSCLE CELLS) (GH AND THYROID NOT NEEDED FOR THIS) zLITTLE EFFECT IN ADULT MEN WITH NORMAL TESTICULAR FUNCTION

GONADAL HORMONES: ESTROGENS zLINEAR GROWTH BEFORE EPIPHYSIS FUSES AND BEFORE BREAST GROWTH (BREAST GROWTH NEEDS HIGHER LEVELS) zMORE COMPLICATED THAN IN MALES

GLUCOCORTICOIDS zACUTELY GIVEN-ENHANCE GH GENE TRANSCRIPTION zCOMPLEX EFFECTS ON GH SECRETION zOVERSECRETION IN CHILDREN MAY RESULT IN STUNTED GROWTH zANTAGONIZE THE ACTIONS OF GH

OTHER HORMONES AND GROWTH FACTORS zEPIDERMAL GROWTH FACTOR zPLATELET-DERIVED GF zTRANSFORMING GROWTH FACTORS zFIBROBLAST GFS zNERVE GF zCYTOKINES zSEE TABLE 1 IN TEXT