Endocrine 2 Flashcards
Insulin Growth Factor 1
Produced in the liver in response to GH, stimulates linear growth by chondrocytes. Inhibits GH secretion.
Insulin Growth Factor 2
Produced in fetal tissues and is important for fetal development.
GH acts indirectly on _____, ______, and _____ via ____.
Organs, chondrocytes, muscle; IGFs.
Overall effects of GH
Decreased adiposity, and increased lean body mass, linear growth, organ size/function.
Effect of GH on protein metabolism
Increases amino acid uptake, decrease urea excretion, promotes protein synthesis.
Effects of GH on carbohydrate and lipid metabolism
Promotes fat usage, increases fatty acid release from the adipose tissue, increases blood glucose levels.
Stimulators of GH secretion
α-andrenergic agonists, low glucose, exercise, stress.
Inhibitors of GH secretion
β-adrenergic agonists.
Ghrelin in GH regulation
Stimulates the hypothalamus to release GHRH and the pituitary to release GH, whilst also inhibiting the release of somatostatin.
IGF-1 in GH regulation
Increases in IGF-1 stimulate the release of somatostatin which decreases the stimulators effects of GHRH on the pituitary. It also inhibits GHRH and GH release directly.
How is GH secreted over the course of 24hrs
Secreted in bursts during the day that increase in size during sleep.
Increased body growth velocity during puberty is associated with ____________.
GH secretion.
Increases in IGF-1 are
GH-dependent! They peak around puberty.
Gigantism
Excess GH during childhood leads to increased growth before the closure of bone growth plates.
Acromegaly characteristics
Disproportionate growth of bones and tissues, enlarged lips/nose/tongue, enlarged mandible - spaced teeth. Deepening of the voice. Fatigue, weakness. Impaired vision (tumour behind eyes).
Acromegaly causes and treatment
95% due to somatotrophic adenoma, treated with surgery or GH-R antagonists/somatostatin agonists.
Deficiency in growth hormone.
No pubertal increase in IGF-1 due to absence of significant GH levels, may or may not be treatable.
Primary GH deficiency
Can be treated with GH supplementation
IGF-1 deletion
GH as a treatment is ineffective as there is no further production of IGF-1 anyways. GH levels will actually be above normal due to the absence of negative feedback signalling.
IGF-1 receptor mutation
Treatment with GH or IGF-1 is ineffective as the receptor on target tissues will not respond anyways.
Action of thyroid hormones
Maturation of the NS, GH synthesis regulation, alertness/reflexes.
Determines basal metabolic rate and facilitates sympathetic activity.
How do thyroid hormones determine basal metabolic rate
Increase ATPase activity, which increases the consumption of ATP, and therefore relies on other fuel sources.
T3 vs T4
The thyroid secretes more T4 than T3. T3 has 10x greater biological activity, and an additional 25μg/day is produced in peripheral tissue by monodeiodination of T4.
Importance of iodine
Thyroid hormones incorporate iodine and it is necessary for their production.
Sources: salt, bread, dairy, shellfish.
Minimum: 75μg/day.
