Growth Hormone Flashcards
GH induces the number of cells by…….., and increases size of cells by……
Stimulating cell division & preventing apoptosis
Favoring synthesis of protein & inhibiting protein degradation
Explain how GH causes bone growth
First: inc in length by chordrogenesis which is followed by ossification & growth of bones by inc protein deposition by chordrocytes and osteogenic cells that cause bone growth, inc rate of reproduction of these cells at the epiphyseal plate of long bones which separates the epiphysis from shaft of long bone.
Second: Growth in thickness, GH strongly stimulates osteoblasts in bone periosteum and some bone cavities which deposit new bone on the surface of older bones.
…….is only stimulated after birth while…….plays a role in fetal growth
IGF-I
IGF-II
Mention metabolic actions of somatomedins
- Have weak insulin-like activity
- Stimulate protein synthesis, growth & chondrogenesis
- They inhibit lipolysis
Describe effects of GH on CHO metabolism
Increase glucose blood level by
1.decreasing its uptake by skeletal muscle & adipose tissue (induce insulin resistance, diabetogenic)
2. Stimulating gluconeogenesis in liver
There is compensatory rise in insulin
Describe effects of GH on lipid metabolism
Ketogenic-lipolytic
Causes release of fatty acids from adipose tissue & inc FA conc in body fluid, also enhances conversion of fatty acids to acetyl CoA & its subsequent utilization for energy. May result in ketosis & fatty liver.
Describe effects of GH on protein metabolism
Enhances all facets of amino acid uptake & protein synthesis while decreasing protein degradation
IGF-I stimulates secretion of……from hypothalamus
Somatostatin
Write a short note on GH diurnal variation
The ant pituitary releases bursts of GH every few hours, its level throughout the day tends to be low & constant. After onset if deep sleep, GH inc upto 5 times its base level, then it rapidly declines over next several hrs.
Mention factors that:
1. Inc GH
2. Dec GH
- a. Deficiency of energy substrates as in hypoglycemia, starvation, fasting, exercise, dec FFA in blood
b. Stressful stimuli
c. Glucagon
d. Inc AAs in blood after protein meal - Hyperglycemia, inc FFA in blood, anging , obesity, cortisol
Gigantism occurs ……union of epiphysis while acromegaly occurs……
Before
After
Mention characteristics of gigantism
- Overgrowth of long bones leading inc height & weight
- Overgrowth of soft tissues
- Enlarged internal organs as hepatomegaly and cardiac hypertrophy
- Hyperglycemia, DM
- Galactorrhea
- Signs of pituitary tumor as visual disturbance, bitemporal hemianopia, projectile vomiting, headache.
- Delayed puberty & hypogonadism
Mention characteristics of acromegaly
- Long bones don’t grow in length, but cartilage & membranous bone continue to grow resulting in deformity
- Overgrowth of soft tissues & viscera (protruded abdomen)
- Kyphosis, enlarged hand & feet
- Lips, tongue, nose, ears & mandible are enlarged (apelike) coarse facial features
- Hypergylcemia, DM
- Galactorrhea
- Signs due to local effects as before
Enumerate causes of pituitary dwarfism
- Inherent GH deficiency
- Hypothalamus disorder
- Organic lesion or surgical removal of pituitary gland
- Secretion of inactive GH
- Lack of end organ response due to receptor defect or failure to secrete somatomedin (Laron dwarfism)
Mention characteristics of dwarfism
- Child growth is arrested, 120 cm
- Symmetrical retardation of bone growth & soft tissue
- Sexual & mental maturation normal
