Somatotropic Axis Flashcards
Main components of the somato tropic axis
Hypothalamus, paraventricular nucleus, GHRH, SRIF, somatotropin’s (GH cells), GH, liver, IGF1, other tissues
GH
Protein hormone with half life of 6-20 min, most abundant AP hormone
Somatomedins
IGFs, polypeptides similar to insulin
IGF1
has systemic and autocrine effects, high at puberty and low later, needed for skeletal and extra-skeletal development and adipocyte differentiation
IGF2
Critical for prenatal development with insulin
GH secretion patterns
Large pulses or peaks 10-30 min in duration, largest occurring 1hr after onset
Lifetime patterns for GH
Highest earliest in life, amplitude and frequency of peaks greatest during pubertal growth spurt and then decline, needed for tissue regeneration in lorded animals
GH transport
Can be transported free but is mostly transported bound to GHBP, which is coded by the same gene as GH-R
IGF1 transport
Bound to IGF-BPs, some of which have endocrine function
Factors that increase GH secretion
Sleep, exercise, hypoglycemia, high dietary protein, steroids, ghrelin
Factors that decrease GH secretion
Hyperglycemia, glucocorticoids, endocrine disruptors
Effect of GH and IGF2 on bones
GH promoters cartilage growth, IGF2 promotes calcification of cartilage cells
Effect of GH and IGF1 on carb and lipid homeostasis
GH is diabetogenic, IGF1 acts similarly to insulin
Effect of GH and IGF1 on protein
Both anabolic
GH and prolactin
GH cross reacts with the prolactin receptor
