Growth Flashcards
What stimulates growth
Hormones
Nutrition
Genetics - determine max height
What hormones are involved in growth
GH IGF-1 Thyroid Androgen + oestrogen Glucocorticosteroid Insulin
What is GH important for in growth
Increases in early years of life
Constant until end of puberty
What stimulates growth in foetal and intial post natal
Nutrient intake
i.e. if gestational DM = large baby
What is thyroid important for in growth
Development of nervous system in utero
Permissive to GH/ IGF-1
What does androgens and oestrogen have on growth
Minor influence until puberty
Produce spike in GH, IGF-1 and bone elongation
Then cause epiphyseal plates to fuse terminating growth
What is cretinism
Hypothyroid at birth
Retarded growth as permissive to GH so GH is normal
Decreased mental capacity
Retain infantile features
How does growth hormone (somatotrophin) work
Peptide hormone
Unusually 50% bound to stop it being excreted as erratic secretion
How does IGF-1 mediate action of GH
Secreted by liver in response to GH
Controls GH release through -ve feedback
Similar to insulin + binds to receptors but GH is more over-riding so causes high BG
What does GH require
Permissive action of thyroid and insulin
Untreateed hypothyroid or poor DM control = stunted growth
What remains constant despite GH variation
IGF-1
What stimulates GHRH release from AP
Actual or potential decrease in energy to cells as GH needed to maintain tissue - Fasting - Hypoglycaemia - Exercise - Cold Increased AA Stress - need Circadian rhythm - Delta sleep Oestrogen / androgen
What increases GHIH
Glucose
FFA
REM
Cortisol
What are effects of GH
Release energy stores to support growth
Maintenance and repair tissue
Increased gluconeogenesis
Reduce insulins ability to stimulate glucose uptake in muscle and fat
Increases lipolysis
Increases AA uptake and protein synthesis
What are the effects of GH / IGF-1 on bone
Stimulates chondrocytes to differentiate and produce cartilage
Bone cells secrete IGF-1
Acts as autocrine and paracrine agent
