Lect 16 - Hypothalamus and Pituitary II Flashcards
Jan 24, 2019
What is the condition called when all pituitary hormones are not released?
panhypopituitarism
Growth hormone deficiency in children leads to…
dwarfism
What is a sign of gigantism on XR?
thickened soft tissue shadows
There are three major effects of panhypopituitarism. What are they?
1) hypothyroidism
2) decreased glucocorticoids
3) decreased sex hormones
What is the half-life of prolactin?
approximately 20 min
What are the three major functions of prolactin?
1) breast development and milk production
2) maintains milk production (but not milk ejection)
3) inhibits ovulation!
Estradiol leads to an increase in prolactin. What is the mechanism for this?
Estradiol inhibits DA which inhibits the hypothalamus. Disinhibition of hypothalamus leads to increased prolactin
At what level does dopamine work in regards to prolactin release?
At the level of lactotrophs in the anterior pituitary
What is the most common pituitary tumor?
Prolactinoma
What causes the visual symptoms related to a pituitary tumor?
impingement on the optic nerve
What is the common visual symptom caused by a pituitary tumor?
bitemporal hemianopsia
A prolactinoma causes amenorrhea, how?
Release of prolactin causes inhibition of ovulation and cessation of menses
What are the three main signs of excess prolactin release?
1) galactorrhea
2) decreased libido
3) inhibition of ovulation/spermatogenesis
How does prolactin inhibit ovulation?
Inhibition of GnRH
What is the medical/symptomatic treatment for a prolactinoma?
Bromocriptine
How does bromocriptine exert its effects on prolactin?
DA agonist
The posterior pituitary _______ two hormones: _______ and _______.
a) stores
b) oxytocin
c) ADH
What is another name for ADH?
vasopressin
Why is vasopressin abbreviated AVP?
short for arginine vasopressin
What are the two triggers that activate the hypothalamus to produce ADH?
1) increase in ECF osmolarity
2) decrease in ECF volume
What is the threshold for ADH release?
~280 mOsm
What are the two main strategies the body has to decrease plasma osmolarity? Which is triggered first?
1) ADH release (triggered first)
2) thirst
Where are V1 receptors found? V2 receptors?
V1Rs found in vascular smooth muscle cells
V2Rs found on principal cells in collecting duct
What are the second messengers present in V1 receptors? V2 receptors?
V1Rs use IP3/DAG/Ca
V2Rs use cAMP
Activation of V2Rs in the collecting duct leads to the incorporation of vesicles of which protein into the membrane?
AQP2 (aquaporin 2)
What disorder is a deficiency of ADH?
diabetes insipidus
How do you differentiate central DI from nephrogenic DI?
Water deprivation, then exogenous ADH; central DI will respond to ADH
What are two symptoms of diabetes insipidus?
1) polyuria
2) polydipsia
