Adrenal Steroids-Burkin Flashcards
What does CRH release? What does TRH release? What do somatostatin & dopamine release?
CRH–>ACTH increases
TRH–>TSH & prolactin increases
somatostatin–>GH decreases
dopamine–>prolactin decreases
When do you get the most GH release? What is its pattern of release?
diurnal 24 hour secretion
highest secretion at night
What is the source of GH?
somatotropes & somatomammotropes of ant pit.
What are the actions of GH?
decreases insulin sensitivity
increases lipolysis
increases IGF-1–>increases protein synthesis & epiphyseal bone growth
What stimulates the release of GH?
GHRH hypoglycemia exercise AA sleep
What inhibits the release of GH?
somatostatin
hyperglycemia
IGF-1 via neg. feedback
What is a major determinant of size in dogs?
IGF-1 allele
What is a possible cause of GH excess?
somatotrope tumor–>can cause gigantism or acromegaly
What is a good treatment for a somatotrope tumor?
surgical removal
somatostatin analogs–octreotide
What are some possible causes of GH deficiency?
hypothalamic or pituitary lesions
GH receptor defect in target tissues-Laron dwarfs
IGF-1 deficiency–African pygmies
What are some possible results of hypothalamic or pituitary lesions, leading to GH deficiency?
dwarfism
adult hypopituitarism–weakness, wrinkly & pale skin, loss of libido, genital atrophy, amenorrhea
What is the treatment for GH deficiency?
GH (somatrophin) & IGF-1 replacement
What are some times when you need to use exogenous GH?
Turner’s syndrome-can increase height
failure to thrive
AIDs wasting–can help treat
increase milk production in cows
WHat are examples of GHRH analogs?
can increase GH release
sermoelin
geref
what is the source of prolactin?
lactotropes & somatomammotropes of ant pit
What are the actions of prolactin?
milk production
maternal behavior
decreases gonadatropin action, decreased steroid production
What stimulates prolactin release? WHat inhibits prolactin release?
stimulated: oxytocin, TRH, VIP, estrogen
inhibited: dopamine
What are some things that can cause hyperprolactinemia?
lactotrope adenoma
dopamine receptor blocker (psychiatric med)
stress/vigorous exercise
What are the effects of hyperprolactinemia in females?
amenorrhea
infertility
galactorrhea
What are the effects of hyperprolactinemia in males?
impotence
infertility
decreased sperm count
What is a good treatment for hyperprolactinemia?
dopamine agonist (bromocryptine)–suppresses prolactin
What does oxytocin released from the post pit do?
stimulates milk production
stimulates uterine contractions
What does ADH release from the post pit do?
increases water absorption
released when BP drops or blood conc’n increases
What happens when you have a deficiency of vasopressin? Treatment?
diabetes insipidus
treated w/ desmopressin acetate
How is GH deficiency diagnosed?
A GH level obtained after 30 mins of exercise was low and a preliminary diagnosis of GHD was made.
10g of arginine 10% I.V. (0.5 g/kg) over 30 mins and later 2 units of regular human insulin IV (0.1 unit/kg) to stimulate GH secretion. GH levels drawn after administration of both agents rose to 3 mg/L (normal is >10). The study was repeated with similar results and a definitive diagnosis of GHD was made.
What is an appropriate treatment for GH deficiency? Good alternative?
use recombinant GH (human)
**alternative–IGF-1
Pt has short stature secondary to GH deficiency. Management?
GHRF (not enough GH coming from ant pit)
sometimes used for patients with height <5th percentile
patients with renal failure
What is Addison’s disease?
partial or complete loss of adrenocortical function
What is Cushing’s disease?
excessive secretion of adrenocorticoid steroids
metabolic disorder
What does pro-opiomelanocortin do?
makes like 8 peptides, including ACTH (39 AA).
What are 2 important domains of ACTH?
activation & binding domain.
Describe the 3 zones of the adrenal cortex & what each secretes.
Outer–Inner
Zona Glomerulosa: Aldosterone
Zona Fasciculata: Cortisol
Zona Reticularis: Androgens
____ mainly targets the fasciculata & reticularis.
____ mainly targets the glomerulosa.
ACTH–>fasciculata & reticularis
Ang II–>glomerulosa
Describe the receptor that binds ACTH in the adrenal cortex.
cell surface G protein receptor
linked to adenylyl cyclase.
More cAMP, which activates protein kinase.
This activation causes increased transport of cholesterol to the mitochondrial matrix & increased steroid synthesis in the long run.
Cholesterol is transported into the mitochondrial matrix & P450scc & becomes other types of steroids. What is the regulator of this ?
StAR
steroidogenic acute regulatory protein
What is the rate limiting step in steroid synthesis?
delivery of cholesterol to mitochondria
T/F The steroid synthetic capacity of the adrenal gland is markedly enhanced by the action of ACTH.
True.
After cholesterol is in the mitochondria w/ P450scc & triggered by ACTH or Ang II…what is produced?
pregnenolone
**that can make 17alpha hydroxypregnenolone (which can go on to be cortisol or androgens) OR make progesterone (which can feed into all 3 pathways)