GH Flashcards
(40 cards)
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?
maximum 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?
- cell division
- 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?
Hypothalamus stimulates 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
