GROWTH HORMONE

D. C. MIKULECKYPROFESSOR OF PHYSIOLOGYANDFACULTY MENTORING PROGRAM

GROWTH

MOST RAPID DURING PRENATAL PERIOD

JUVENILE PERIOD: GH IS VERY IMPORTANT, BUT ALSO INSULIN AND THYROID HOMONE

ADOLESCENT: ANDROGENS AND ESTROGENS AS WELL-SPEED UP GROWTH AND BRING BONE GROWTH TO A HALT

CONTROL OF GROWTH

GENETIC POTENTIALDIETDISEASEHORMONES

ANTERIOR PITUITARY HORMONES: GROWTH HORMONE (SOMATOTROPIN)

LIVERSOMATOMEDINSBONESOFT TISSUEGROWTH(ABOUT

30% OF THE GENETIC POTENTIAL)

MANY TISSUES INTERMEDIARY

METABOLISM INCREASE OR

DECREASE

GROWTH HORMONE: SYNTHESIS, SECRETION, AND METABOLISM

ABOUT 1/6 OF THE AP CELLS 5 - 10 MG STORED 10X ANY OTHER PITUITARY HORMONE TWO FORMS 22K AND 20K BOUND TO PROTEIN IN BLOOD (SAME

COMPOSITION AS RECEPTOR) CANNOT ENTER CELL DEGRADED IN TARGET CELLS AFTER UPTAKE

BY RECEPTOR MEDIATED PROCESS

METABOLIC ACTIONS OF GROWTH HORMONE

DECREASES SENSITIVITY OF MUSCLE AND FAT CELLS TO INSULIN

SENSITIZES BETA CELLS TO SIGNALS FOR INSULIN SECRETION (GET PROTEIN SYNTHESIS WITHOUTDECREASE IN BLOOD GLUCOSE)

MOBILIZES TRIGLYCERIDE FAT STORED IN ADIPOSE TISSUE

CONSERVES GLUCOSE FOR BRAIN DIABETOGENIC EFFECT

GH AND AGE

SECRETED THROUGHOUT LIFERATE DECREASES FROM 20-40MAY ACCOUNT FOR LOSS OF

BODY MASS IN THE ELDERLYCHANGES OCCUR IN BOTH

FREQUENCY AND MAGNITUDE OF SECRETIONS

GROWTH PROMOTING ACTIONS OF GROWTH HORMONE

SOFT TISSUES: STIMULATES CELL DIVISION, INCREASES SIZE OF CELLS

STIMULATES ALMOST ALL ASPECTS OF PROTEIN SYNTHESIS

INHIBITS PROTEIN DEGRADATIONPROMOTES UPTAKE OF AMINO

ACIDS

GROWTH PROMOTING ACTIONS OF GROWTH HORMONE

BONE: PROMOTES GROWTH OF LONG BONES

THICKNESSLENGTHAT END OF ADOLESCENCE, SEX

HORMONES STOP THIS ACTION

GROWTH HORMONE ACTS THROUGH SOMATOMEDINS

PEPTIDE MEDIATORS: SOMATOMEDINS

CLOSELY RELATED TO INSULIN-LIKE GROWTH FACTORS IGF-I AND IGF-II

PRODUCED IN LIVER AND OTHER TISSUES

ALSO PARACRINE EFFECTS

REGULATION OF GROWTH HORMONE SECRETION

HIGHER BRAIN CENTERS

(+) (-)

HYPOTHALAMUS

GH-RH SST

PITUITARY

TARGET CELLS

GH SOMATOMEDINS

GHRH AND GHIH

ANTAGONIST IN CONTROL OF GROWTH HORMONE SECRETION

NEGATIVE FEEDBACKDIURNAL RHYTHM: GH SECRETED

AT NIGHTEXERCISE, STRESS,

HYPOGLYCEMIA

ABNORMAL GH SECRETION

DEFICIENCY: DWARFISM, REDUCED MUSCLE STRENGTH, DECREASED BONE DENSITY

EXCESS:GIGANTISM, ACROMEGLY

EPINEPHRINE, CORTISOL, AND GROWTH HORMONE

ALL INCREASE BLOOD GLUCOSE AND FATTY ACIDS

CORTISOL INCREASES BLOOD AA AND DECREASES MUSCLE PROTEIN

GH DECREASES BLOOD AA AND INCREASES MUSCLE PROTEIN

EFFECTS OF GROWTH HORMONE ON BODY COMPOSITION

DEFICIENCY PROMOTES HIGHER PERCENTAGE OF FAT

PROMOTES GROWTH OF MUSCLE, SKIN, HEART, AND MOST INTERNAL ORGANS EXCEPT LIVER, SPLEEN, THYROID, GONADS, OR REPRODUCTIVE ORGANS.

SYNERGISM OF GH WITH OTHER HORMONES

THYROIDINSULINGONADAL HORMONESGLUCOCORTICOIDSOTHER HORMONES AND

GROWTH FACTORS

THYROID AND GROWTH

GROWTH STUNTED IN ABSENCEEXCESS MAY STIMULATE RATE

BUT NOT DRAMATICALLYPROMOTE GH SYNTHESISPERMISSIVE EFFECT ON GH AT

TARGETS

INSULIN

IMPORTANT DURING FETAL PERIOD IN CONTRAST TO GH AND THYROXINE

CHILDREN OF DIABETIC MOTHERS CAN BE LARGER

RELATED STRUCTURALLY TO THE SOMATOMEDINS

WITHOUT INSULIN, NORMAL RESPONSES TO GH ARE NOT SEEN

REGULATOR OF PROTEIN SYSNTHESIS? REGULATOR OF ENERGY METABOLISM

GONADAL HORMONES: ANDROGENS

LINEAR GROWTH BEFORE EPIPHYSIS FUSES ENHANCED GH SECRETION GROWTH OF MUSCLE: DOUBLING OF

MUSCLE MASS IN BOYS AT PUBERTY (SIZE AND NUMBER OF MUSCLE CELLS) (GH AND THYROID NOT NEEDED FOR THIS)

LITTLE EFFECT IN ADULT MEN WITH NORMAL TESTICULAR FUNCTION

GONADAL HORMONES: ESTROGENS

LINEAR GROWTH BEFORE EPIPHYSIS FUSES AND BEFORE BREAST GROWTH (BREAST GROWTH NEEDS HIGHER LEVELS)

MORE COMPLICATED THAN IN MALES

GLUCOCORTICOIDS

ACUTELY GIVEN-ENHANCE GH GENE TRANSCRIPTION

COMPLEX EFFECTS ON GH SECRETION

OVERSECRETION IN CHILDREN MAY RESULT IN STUNTED GROWTH

ANTAGONIZE THE ACTIONS OF GH

OTHER HORMONES AND GROWTH FACTORS

EPIDERMAL GROWTH FACTORPLATELET-DERIVED GFTRANSFORMING GROWTH FACTORSFIBROBLAST GFSNERVE GFCYTOKINESSEE TABLE 1 IN TEXT