Growth HarmoneGrowth Harmone

Learning Objectives

  • By the end of lecture, students should
    be able to
  • Mention the source of growth
  • State the release and regulation of
    growth hormone
  • Summarize the metabolic and
    growth effects of growth hormone
  • Explain the role of somatomedin C
  • Explain the abnormalities related to
    growth hormone


  • A mother and father bring there child of 7
    years old to their new pediatrician
    concerned with their son’s growth. The
    parents say he is shorter than both the
    males and females in his class and seems
    to have lower muscle strength and mass in
    comparison with his peers. The doctor
    takes measurements and finds that their
    son is approximately 22% shorter than the
    average male height at his age. The doctor
    also notes that despite the shorter height,
    the body and limb proportions are
    relatively normal, though there is an
    increased distribution of fat throughout
    the body

Growth Hormone

  • Growth hormone, also called somatotropic
    hormone or somatotropin
  • Small protein molecule contains 191 amino
    acids in a single chain
  • Molecular weight of 22,000.
  • Causes growth of almost all tissues of the
  • Promotes
  • Increase in size of the cells and increased
  • Development of greater numbers of cells
  • Specific differentiation of cells such as
    bone cells and muscle cells.
  • Growth hormone receptor—620
    amino acid protein
  • Transmembranous protein
  • Acts via enzyme activation—
    intracellular signaling pathway
  • Plasma concentration– 0-3ng/mL
  • Increased rate of protein synthesis in most
    cells of the body
  • Increased mobilization of fatty acids from
    adipose tissue
  • Increased free fatty acids in the blood, and
    increased use of fatty acids for energy;
  • Decreased rate of glucose utilization
    throughout the body.
    Growth hormone enhances body protein, uses
    up fat stores, and conserves carbohydrates

Protein Metabolism (Anabolic)

Growth Hormone

  • Enhances transport of amino acids into the interior of
    the cells
  • Increases the amino acid concentrations in the cells
    results in increased protein synthesis
  • Stimulates the transcription of DNA in the nucleus leads
    to formation of increased quantities of RNA
  • Increases RNA translation, causing protein to be
    synthesized in greater amounts by the ribosomes in the
  • Restricts catabolism thus decreases the breakdown of
    cell protein
  • Mobilizes free fatty acids from adipose tissue to supply
    energy to the body cells, thus a potent “protein sparer.”

Fat Metabolism (Ketogenic)

Growth Hormone

  • Causes release of fatty acids from adipose
    tissue thus increasing the concentration of
    fatty acids in the body fluids
  • Enhances conversion of fatty acids to acetyl-
    CoA and its utilization for energy
  • Increase lean body mass
  • Large quantities of acetoacetic acid (ketone
    body) formed by liver and released into the
    body fluids, causing ketosis
  • Can cause fatty liver

Carbohydrate Metabolism (Diabetogenic)

Growth Hormone

  1. Decreases glucose uptake in tissues such
    as skeletal muscle and fat
  2. Increases glucose production by the liver
  3. Increased insulin secretion.
  • Growth hormone–induced “insulin
  • Growth hormone decreases insulin’s actions
  • uptake and utilization of glucose in skeletal
    muscle and adipose tissue
  • To inhibit gluconeogenesis by the liver
  • Leads to increased blood glucose
    concentration and compensatory increase in
    insulin secretion
  • Mechanism for increased blood glucose is
  • Probably increase free fatty acids reduce
    sensitivity of the cells to insulin effects
  • Adequate insulin activity and adequate
    availability of carbohydrates are required for
  • Insulin promotes transport of amino acid
    into the cells

Cartilage and Bone Growth

Growth Hormone

  1. Increases deposition of protein by the
    chondrocytic and osteogenic cells that
    cause bone growth,
  2. Increased rate of reproduction of these
  3. Conversion of chondrocytes into
    osteogenic cells, thus causing deposition
    of new bone.
  • Long bones grow in length at the epiphyseal
  • Growth hormone causes deposition of new
    cartilage initially and followed by its
    conversion into new bone
  • Results in lengthening of the shaft and
    pushing the epiphyses farther
  • GH stimulates osteoblasts thus makes bones
    thicker throughout life
  • Thickening of bones- membranous bones.
  • Jaw bones – forward protrusion of the chin and
    lower teeth.
  • The skull – bony protrusions over the eyes

Somatomedins – IGF

  • GH causes the liver and other tissues to form
    several small proteins called somatomedins
  • Also known as insulin like growth factors
  • Potent effect of increasing bone growth– IGFs
  • 4 somatomedins – somatomedin C (IGF-I),
    molecular weight 7500
  • Pygmies of Africa have congenital inability to
    synthesize somatomedin C
  • Plasma concentration of GH is either normal or
    high but diminished amounts of somatomedin C
    in plasma- have small stature
  • Known as Lévi-Lorain dwarf


GH half life less than 20 minutes – somatomedin C half life 20 hours

Regulation of GH Secretion

Regulation of GH

Regulation of Growth Hormone

Role of the Hypothalamus

  • Release of growth hormone is controlled by growth hormone releasing hormone(GHRH) and growth hormone inhibitory hormone(GHIH)
  • Hypothalamic nucleus that causes secretion of GHRH is the ventromedial nucleus
  • Similar area that is sensitive to blood glucose concentration, causing satiety in hyperglycemic states and hunger in hypoglycemic states
  • GHRH predominates over GHIH

Growth Hormone – Abnormalities

GIGANTISM– over secretion of growth hormone before puberty

ACROMEGALY– over secretion of growth hormone after puberty

  • Alam Channa– shrine of sufi saint—height was 7 feet 6
  • Giant Gonzalez- Jorge González– a Basketball player
    &Wrestler– massive height of 7 feet 6 inches
  • The Great Khali -Dalip Singh Rana, an Indian
    professional wrestler, actor and powerlifter– height is
    7 Feet 1 inch
  • The Big Show- Paul Donald Wight is an American
    professional wrestler– height – 7 feet
  • Maurice Tillet- French Wrestler after whom the Ogre
    character Shrek is said to be created, suffered from
    acromegaly. Since his problem started late, he could
    not gain extra height like other. He measured 1.7

Growth Hormone

  • DWARFISM under secretion of growth
  • The Little Couple– American reality
    television series features Bill Klein and
    Jennifer Arnold, who both have
    skeletal dysplasias. Arnold is 96.5 cm
    (3’2″) and Klein 122 cm (4 feet) tall
  • Jen is a pediatrician and completed
    masters of medical education

Panhypopituitarism in Adults

  • Panhypopituitarism – decreased secretion of
    all the anterior pituitary hormones –
    congenital or pituitary tumor
  • Craniopharyngiomas or chromophobe
    tumors compress the pituitary gland
  • Thrombosis of the pituitary blood vessels
  • when a new mother develops
    circulatory shock after the birth of her
    baby – sheehan’s syndrome

Panhypopituitarism in Adults


  1. Hypothyroidism
  2. Lethargic person
  3. Depressed production of glucocorticoids
  4. Sexual functions are lost due to
    suppressed secretion gonadotropic
  5. Weight gain – lack of fat mobilization by
    growth, adrenocorticotropic and thyroid
  • Administration of adrenocortical and thyroid

Applied– Under secretion

  • Dwarfism
  • Generalized deficiency of anterior pituitary
    hormones in childhood
  • Rate of development decreased, growth
    affected in a proportionate manner
  • Not pass through puberty and never secretes
    sufficient quantities of gonadotropic
    hormones to develop adult sexual functions.
  • Only GH is deficient – mature sexually and
    occasionally reproduce
  • African pygmy and the Lévi-Lorain dwarf (IGF
  • Treatment
  • Human GH – synthesized by E. coli bacteria
    as a result of recombinant DNA technology

Applied– Over secretion

  • Gigantism
  • Before puberty– over secretion of growth
  • Acidophilic tumors
  • All body tissues grow rapidly
  • 8 feet giant
  • Hyperglycemia – DM
  • Death can occur in early adulthood
  • Treatment
  • Microsurgical removal of the tumor
  • By irradiation of the pituitary gland


  • Acidophilic tumor– after puberty
  • Effects
  • Cannot grow taller epiphysis has fused
  • Bones become thicker
  • Soft tissues continue to grow.
  • Bones of the hands and feet – membranous
    bones, like cranium, nose, forehead, supraorbital
    ridges, lower jaw bone, vertebrae
  • Lower jaw and forehead protrudes forward
  • Nose increases twice normal size
  • Feet require size 14 or larger shoes
  • Fingers thickened and hands are twice normal
  • Vertebrae bent back, kyphosis
  • Large tongue – liver, kidneys, enlarged

Maurice Tillet–Oregon shrek

GH & Aging

  • 50-year-old person without GH for
    years looks like person aged 65
  • Reason
  • Decreased protein deposition in
    most tissues of the body
  • Increased fat deposition
  • Increased wrinkling of the skin
  • Diminished rates of function of
    some of the organs
  • Diminished muscle mass and

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