Flashcards in GH Deck (40):
What does growth hormone do?
-Continous net protein synthesis in children
-increases in length, diameter, and size and number of cells in the soft tissues in long bones
-essential for growth
Characteristics of fetal growth?
- placental GH plays no role in fetal growth before birth
-fetal growth is promoted by certain hormones in the placenta
-after birth, non-placental GH kicks in
-genetic and nutritional factors affects fetal growth
linear growth is:
a marked acceleration due to the lengthening of long bones during puberty
What does an increase of testosterone during puberty do for boys?
contributes to growth by promoting protein synthesis and bone growth
Both testosterone and estrogen contribute to what during puberty
contribute to achieving full adult height by the end of adolescence
what do genetic factors determine according to growth?
An adequate diet for growth promotion includes
- enough protein and essential amino acids to accomplish the protein synthesis necessary for growth
What can an inadequate diet do to growth?
Inadequate diet in infancy and childhood can stunt growth and brain development
-70% of total brain growth occurs during the first 2 years of life
what does stress and cortisol do to growth?
-prolonged stress-induced cortisol can adversely affect growth
-cortisol acts an anti-growth hormone by protein breakdown, inhibiting growth of long bones and blocking GH secretion
What other hormones influence GH secretion?
Thyroid, sex hormones, and insulin affects Gh secretion and growth
How is bone thickness achieved?
-achieved by adding new bone cells by osteoblasts within the periosteum
thickness is produced by osteoblasts within the periosteum (connective tissue that covers outer bone)
-osteoblast activity deposits new bone cells on the exterior of the bone
-osteoclasts (bone breakers) dissolve bony tissue on the inner surface next to the marrow cavity, so the marrow cavity can enlarge
How is growth in length (linear) accomplished?
-growth in length is accomplished by the activity of cartilage cells (chondrocytes), in the epiphyseal plates
-Division and multiplication of chondrocytes on the outer edge of the epiphyseil plate
GH stimulates growth of soft tissue and skeleton by: (two)
1) increasing the # of cells (hyperplasia)
2) increasing the size of cells (hypertrophy)
How does GH increase size and number of soft tissue?
-preventing apoptosis (programmed cell death)
-increases protein synthesis (uptake of amino acids by cells)
-stimulates the cellular machinery according to genetic code to accomplish protein synthesis
Negative feedback of GH?
Hypophtiotrophic hormones which triggers
anterior pituitary to secrete
GH which targets
target tissue and endocrine gland
-Target Tissue stimulation shuts down
What stimulates growth?
Somatomedin (IGF-1) (produced by liver)
-The effects of GH are brought about by this
-Structure and function is similar to insulin
How does somatomedin act of growth?
-acts directly on bone and soft tissue to bring about growth factors
-stimulates protein synthesis, cell divison, and lengthening and thickening of bones
what metabolic effects does somatomedin exert that is not related to growth?
-Increases fatty acid levels in blood by enhancing breakdown of triglycerides/ fat storage in adipose tissue
-increases blood glucose levels by decreasing glucose uptake by muscles
what is IGF-1?
-stimulated by GH
-depends on adequate nutrition
-influenced by age-related factors
-influenced by sex hormones
is produced locally by target tissue and acts as a paracrine means
what is IGF-2?
-stimulated by GH
-does not depend on GH level
-Important in fetal development
-role in adult is ujnclear
what actions do IGF-1 do?
-increase cell division
-increase protein synthesis
(decrease blood amino acids)
-increase bone growth
what actions do IGF-2 do?
-increase fat breakdown (increase blood fatty acids)
-decrease glucose uptake by muscles (increase blood glucose)
-increases glucose uptake by liver (increase blood glucose)
Why do children grow by adults stop growing? How does age influence IGF-1 production?
-due to local production of IGF than blood born IGF
-a huge increase in circulating IGF-1 level accompanies the moderate increase in GH at puberty
How does nutrition influence IGF-1 production?
inadequate food intake decreases IGF level through sensitivity to GH in tissue that produces IGF-1
-ex, fasting decreases IGF-1 level but increases GH secretion
How does tissue stimulating factors influence IGF-1 production?
- increases IGF01 production in particular tissue
-ex, gonadotropin and sex organs stimulate IGF-1 in testes, the ovaries, and uterus
What are factors that influence GHG secretion?
-GhFH/ GHIH (hypothalamus)
-Excercise, stress and hypoglycemia
How does GHRH and GHIH influence GH secretion?
-they both increase GH secretion
-negative feedback loop regulates it
-somatomedins (liver) influences the A.pitiitary to inhibit the effects of GHRH on GH release
Hoe do diumal rhythms influence GH secretion?
- Gh levels tend to be low and constant most of the day
-it is 5 times higher one hour after deep sleep and drops over the next several hours
how does exercise, stress, and hypoglycemia influence GH secretion?
- all of these factors increase GH secretion
-Gh uses fat storage and promotes body protein synthesis during stressful situations
- decreases body fat during exercise may partly mediate an increase of GH secretion during exercise
How does amino acids influence GH secretion
-increased amino acid level after high protein meal increases GH secretion
- decreases in blood fatty acid stimulates GH release
-Gh has fat-mobilizing ability to maintain constant blood fatty acid levels
What are GH secretion disorders?
Symptoms of dwarfism?
-Hyposecretion in childhood
short stature caused by retarded skeletal growth
-poor developed musculature
-excess subcutaneous fat (less fat mobilization)
causes of dwarfism?
Lack of GH from the a. pituitary
-lack of GHRH
Causes and symptoms of Laron dwarfism?
-failure of a tissue to respond to GH
-GH receptors are unresponsive to GH
-reduced skeletal muscle mass and decreased bone density in adults
-risk of developing heart failure
causes and symptoms of gigantism?
-A tumor of the GH producing cells of the a.pituitary
-overproduction of GH in childhood before epiphyseal plate closes
-individuals may reach a height of 8 feet or more
causes of Acromegaly?
-hypersecretion of GH after adolescents before epiphyseal plate close, further growth is prevented
Symptoms of Acromegaly?
1. Excessive GH secretion causes thickening of soft tissues such as skin, thickening of bone in the extremities & face.
2. Jaw & cheekbones thickens and fuses, giving ape-like appearance.
3. Hands, feet enlarge, and finger & toes become thick.
4. Overgrown connective tissue trap the nerves giving peripheral nerve disorder.
5. May result in visual disturbances.
What is the thyriod hormones role in growth?
- it is essential for normal growth but does not promote the growth
-plays a permissive role in skeletal growth, promotes its role in GH presence
-hypothyroic children exhibit stunted growth
What is insulins role in growth?
-serves as a growth promotor
-hyperinsulinemia increases growth and deficiency reveres it
-it may partly exerts its effects via ICF-1 receptors as both receptors appear to be similar in structure