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23 Cards in this Set

  • Front
  • Back
What are the 3 chemical classifications of hormones?
Amino acid derivatives, peptides, steroids
Steroid hormones are stored in the cytoplasm until release.
False: steroids diffuse freely through the membrane as they are being made
What are the average half-lives of steroid and peptide hormones? What is the clinical significance?
Steroids: 4-120 min
Peptides: 4-30 min
Impaired clearance can lead to dangerous accumulation
What are the 6 major hormones secreted by the anterior pituitary?
What is the structure of FSH, TSH, and LH?
They are glycoproteins with identical a-subunits and hormone-specific b-subunits.
What hormone inhibits the release of GH?
What is long loop feedback?
The hormone released by the target organ inhibits the hypothalamus and anterior pituitary.
What is short loop feedback?
The hormone released by the anterior pituitary inhibits the hypothalamus.
What is the ultrashort feedback loop?
The hormone released by the hypothalamus inhibits its own further release.
GH is required for normal growth and normal fetal development.
False: GH is req'd for normal growth but not normal fetal development.
How does GH normally travel in circulation?
Bound to GHBP.
Where is IGF-1 synthesized? What stimulates its expression?
In the liver.
What is the relationship of IGF-1 to insulin?
Its prescursor resembles proinsulin; there is some cross-binding with insulin receptors, esp. in pts who are insulin resistant.
What effects of GH are mediated by IGF-1?
Its growth-promoting effects:
*chondrogenesis in long bones
*growth of soft tissues
Does IGF-1 circulate free in the plasma or bound to carrier proteins?
Despite being freely soluble, IGF-1 circulates bound to many different proteins, some of which enhance its action, some of which attenuate its action.
What are the direct metabolic effects of GH?
They are "anti-insulin":
*increase lipolysis in adipocytes
*increase blood glc thru breakdown of CHO and proteins
Describe the release of GH. Is it constant? What stimulates it?
GH release is stimulated by GHRH and inhibited by SS. The balance between these results in pulsatile synthesis and secretion. Most bursts are nocturnal and occur during REM sleep.
How are GHRH and SS regulated?
Circulating GH and IGF-1 inhibits GHRH and stimulates SS.
What is the result of GH deficiency and how is it treated?
Pituitary dwarfism; treated with recombinant hGH
What does excess GH cause?
Describe the average levels of GH over the lifespan.
Highest level in children, begins to taper after 40, which contributes to body and metabolism changes in middle age.
What are four benefits to GH replacement tx in older adults?
1.Increased lean body mass
2.Decreased fat mass
3.Increased SV and cardiac performance
4.Improved mood and vitality
What is a risk in GH replacement tx?
Increased levels of IGF-1 which is a potent mitogen and potential carcinogen.