Anterior and Posterior pituitary; Growth Hormone Flashcards
What’s the difference in how neurons signal between the anterior and posterior pituitary?
For posterior pituitary, neurons project directly into the gland and the hormones travel to the bloodstream via the capillary bed
For the anterior pituitary, the neurons don’t project into the ant pit; hormone factors are released into the portal plexus (in the median eminence) then they drift into the ant pit
Name the anterior pituitary hormones, the type of hormone each is, and the cell types that release them
LH and FSH: gonandotrophs; glycoprotein
TSH: thyrotrophs; glycoprotein
GH: somatotrophs (somatomammotrophic)
PRL: lacto/mammotrophs (somatomammotrophic)
ACTH: corticotrophs (POMC derivative)
What are the releasing hormones for the following:
TSH
LH/FSH
GH
ACTH
What are the 2 functions of the releasing hormones? By which mechanism are they activated? T/F: GH and PRL are the exception to this mechanism.
Thyrotropin releasing hormone (TRH) - TSH
Gonadotropin releasing hormone (GnRH) - LH, FSH
Corticotropin releasing hormone (CRH) - ACTH
Growth hormone releasing hormone (GHRH) - GH
Activated via GPCR signaling
True. PRL and GH have a separate pathway
What are the roles of somatostatin and doPamine? (i.e. which hormones do they act on and how)
Somatostatin inhibits GH
Dopamine inhibits Prolactin
Describe the loop below. Give three examples of hormones and target organs involved at each level.
Describe the difference between long, short and ultra short feedback in the hypothalamic-pituitary loop
Long feedback – endocrine hormone feeds back on pituitary and hypothalamus
Short feedback – pituitary hormone feeds back on hypothalamus
Ultra-short feedback – hypothalamic releasing factors feed back on the hypothalamus itself
What are the three hypothalamic axes discussed?
HPG (gonadal) axis
HPA (adrenal) axis
HPT (thyroid) axis
Outline the HPG axis. Which hormones are involved at each level?
What are the functions of LH and FSH in men and women? Between FSH and LH, which one would you test and why?
LH - ovulation, testosterone production
FSH - follicle growth, spermatogenesis
(see diagram below)
Test FSH b/c release is more stable. LH has more pulsatility
What are the effects of pulsatile vs continuous GnRH release? (refer to diagram below)
What’s an example disorder that can be treated by continuous GnRH release?
Continuous release of GnRH – eventually, GnRH receptors are downregulated
Pulsatile release: axis functions like its supposed to
Prolonged GnRH can be used to treat precocious puberty because gonadal axis is suppressed
Describe the HPA axis (plus hormones involved and all that)
What is the effect of CRH on ACTH release and POMC?
What other hormone is formed from ACTH breakdown whose product clues us into a low cortisol/high ACTH problem,like primary adrenal insufficiency?
ACTH and other POMC derived peptides secreted; POMC transcription increased
Melanocyte stimulating hormone (MSH) (hyperpigmentation present in primary adrenal insufficiency)
Subclinical hypo vs hyperthyroidism
Subclinical hypothyroidism (TSH levels slightly high but thyroid levels normal)
subclinical hyperthyroidism (TSH levels slightly low but thyroid levels normal)
Describe the HPT axis.
How are hypothyroidism and prolactin related? (think TSH/T4 levels and downstream effects)
Outline the pathway of GH release.
Which factors stimulate GH release? What inhibits it?
What are the functions of GH? What’s the effect of GH excess?
Stimulated by Ghrelin, free fatty acids
Inhibited by STS
Regulated by IGF1
GH excess = insulin resistance, acromegaly
Relationship between GH and PRL.
What kinds of receptors do they act on? (hint: not GPCRs like the other ones)
Structurally similar, both can be released sometimes (esp by a tumor); GH can activate PRL receptors at high conc but not vice versa
Act on Cytokine receptors
What stimulates PRL release? What inhibits it? Which effect is mostly present?
What’s the main PRL function?
Describe the stalk effect and what happens to dopamine release
Stimulated by estrogen, TRH
Inhibited by dopamine (main effect)
Function = lactation
Stalk effect = inhibition of pituitary stalk, which blocks dopamine effect (other hormones also decreased) >> increased PRL