Hormonal regulation of growth Flashcards
- Describe the mechanism of synthesis and secretion of GH - Identify the factors influencing GH secretion - Describe the metabolic effects of GH - Describe the relationship between GH and insulin-like growth factors - Describe hormones affectiving growth beside GH - Identify factors influencing growth beside GH - Outline the types and pathophysiology of GH abnormalities
1
Q
Hormones that stimulate growth
A
- thyroid hormone
- insulin
- testosterone
- oestrogens
- growth hormone -> principle
- insulin-like growth factor
- calcitonin, PTH, and vit D
2
Q
Regulation at growth stages
A
Prenatal -> maternal factors, fetal insulin and IGF-1
Infancy -> genetic factors, GH production, thyroid hormone, IGF-1
Adolescence -> GH, insulin, IGF-1, and sex hormone surge
3
Q
Growth hormone (GH)
A
- released from somatotrophs of anterior pituitary in response to release of GHRH
- regulates metabolism directly and indirectly
- manufactured as preprohormone in rough ER
- loaded into secretory granules in Golgi
4
Q
Secretion of GH
A
- stimulated by GHRH release from arcuate nucleus
- inhibitory to somatostatin
- upregulation of cAMP, activation of PKA
- phosphorylation of calcium channels, drives exocytosis of secretory granules releasing GH
5
Q
GHIH
A
- somatostatin is released from periventricular region
- somatostatin acts on somatotrophs
- somatostatin receptor acts as negative regulator of Adenylyl cyclase, decreasing cAMP, decreasing PKA, decreasing phosphorylation and decreasing intracellular Ca concentration
6
Q
Decrease GH secretion
A
- IGF-1 -> primary mechanism negative feedback
- GH secretion negatively feeds back on somatotrophs
- hyperglycaemia
- obesity
7
Q
Increase GH secretion
A
- stress
- high protein meals
- exercise
- hypoglycaemia
- ghrelin
8
Q
Role of GH on liver in fed state
A
- increased RNA synthesis
- increased IGFs
9
Q
Role of GH in muscle in fed state
A
- increased AA uptake
- increased protein synthesis
10
Q
Role of GH in fed state in bone, heart and lung in fed state
A
- increased protein synthesis
- increased RNA synthesis
- increased DNA synthesis
- increased cell size and number
11
Q
Roles of GH in Chondrocytes in fed state
A
- increased AA uptake
- increased protein synthesis
- increased RNA synthesis
- increased DNA synthesis
- increased collagen
- increased chondroitin sulfate
- increased cell size and number
12
Q
Role of GH on adipose tissue in fasted state
A
- decrease glucose uptake
- increased lipolysis
13
Q
Role of GH on muscle in fasted state
A
- decreased glucose uptake
14
Q
Role of GH on liver in fasted state
A
- increased gluconeogenesis
15
Q
Direct effects of GH
A
- binds directly to target cells (liver, muscle, adipose)
- antagonises the effects of insulin
- removal of pituitary (source of GH) -> facilitates better control of blood glucose in diabetes
- stimulates growth (hypertrophy)
- stimulates cell reproduction (hyperplasia)
