principles of endocrinology

Question 1

hormone transport: protein

Answer 1

stored within intracellular vesicles; secreted into blood as required; short-lived so short-lived action

Question 2

what is the active pool of steroid hormones

Answer 2

those not bound to binding proteins

Question 3

why is it at equilibrium

Answer 3

so when free hormone is utilised, it is restored by stored hormone release, followed by stimulus to endocrine cells to cause adjustments of hormone secretion rates so free hormone available to tissues remains constant; changing plasma protein concentration also alters equilibrium (causes more hormone to be bound; e.g. CBG levels in pregnancy increase so cortisol levels rise so constant level of free hormone available)

Question 4

peptide hormone signalling: process

Answer 4

G-protein coupled receptor activated by dissociation of the a subunit; activates secondary messenger (adenylate cyclase, increase cAMP levels, binds to cAMP dependent protein kinases - activates cholesterol esterase to converty cholesterol esters to free cholesterol/activates StAR protein to mediate transfer of cholesterol)

Question 5

where are steroid hormone targets and why

Answer 5

within the cell as are lipid soluble so can diffuse through membrane

Question 6

steroid hormone signalling: process

Answer 6

hormone-receptor complex travels to nucleus and binds to specific DNA binding sites, leading to change in specific gene transcription rates; powerful but slow-acting