172b/173b/175b - Hypothalamus/Pituitary Basics, Histo, Path, Pathophys Flashcards
Which nuclei of the hypothalamus secrete TRH and GnRH? (3
Paraventricular
Ventromedial
Dorsal nucleus
What substances are secreted by the arcuate nucleus of the hypothalamus? (3)
GHRH
Dopamine
GnRH
What causes Laron’s syndrome?
What is the treatment?
Defective growth hormone receptor -> GH insensitivity
-> Cannot generate IGF-1 in response
Treatement: Give IGF-1 analog (mecasermin)
What is the difference between Cushing Syndrome and Cushing Disease?
-
Cushing Syndrome
- Hypercortisolism of any etiology
-
Cushing Disease
- Hypercortisolism due to ATCH pituitary adenoma
What is the embryonic tissue of origin for the anterior pituitary?
Posterior pituitary?
Anterior: Oral cavity ectoderm (Rathke pouch)
Posterior: Neuroectoderm (diencephalon)
List the 4 sites of action of Growth Hormone (GH)
(general)
- Linear growth (epiphyseal plate via IGF-1 modulation)
- Bone
- Muscle
- Adipose tissue
The biopsy of this sellar lesion from a 35-year-old postpartum woman is most consistent with which of the following statements?
- This was a normal change
- This was caused by hypertension, and elevated intracranial pressure
- The portal venous circulation from hypothalamus was compromised
- The small arteriole branches from the posterior pituitary were compromised
c. The portal venous circulation from hypothalamus was compromised
- Sheehan syndrome
- Postpartum bleeding
- > hypotension
- > infarct of the anterior pituitary
What substances are secreted by the dorsal nucleus of the hypothalamus? (2)
TRH
GnRH
Which two pituitary hormones are negatively regulated by somatostatin?
Growth hormone (GH)
Thyroid stimulating hormone (TSH)
Which portion of the pituitary contains axons?
Where do they originate?
Posterior pituitary
Axons originate in neurons in the supraoptic (ADH) and paraventricular (oxytocin) nuclei of the hypothalamus
What class of receptor is the vasopressin receptor?
GPCR
- V1 = Gq
- V2 = Gs
What is the most common sellar mass?
Craniopharyngioma
Which pituitary adenoma is most likely to present as a microadenoma?
ACTH-producing
Often symptomatic, presents when small
How do you expect the following to change as plasma vasopressin levels increase?
- Urine output:
- Urine osmolarity:
- Urine output: Decreases
- Urine osmolarity: Increases
What hypothalamic hormone inhibits the release of growth hormone?
Where is it released?
Somatostatin
Paraventricular nucelus
What are the two receptors for vasopressin (ADH)?
What happens when they are activated?
-
V1 in vascular endothelium and smooth muscle
- Increases smooth muscle contraction
- > Increased BP
-
V2 in the basolateral membrane of collecting tubules
- Insertion of AQP2 into the luminal membrane
- > Reduce urinary water excretion
-
V2 outside of the kidney
- Increases release of Factor VIII and vWF
- > platelet aggregation
What is the treatment for prolactinoma?
Bromocriptine
Cabergoline
(Dopamine receptor agonists)
How are GPCRs desensitized and downregulated?
- Phosphorylation
- Endocytosis
- Degradation -> permanent signal termination
A 27 year old woman who had been previously well has developed amenorrhea (loss of menses) and galactorrhea. Which one of the following hormones might you expect to be elevated?
a. Growth hormone
b. Vasopressin
c. Prolactin
d. ACTH
e. Luteinizing Hormone
c. Prolactin
Which drug is a growth hormone receptor antagonist?
Pegvisomant
What are the two major stimuli for oxytocin release?
- Suckling (breast feeding)
- Cervical stretch (during labor)
-> Oxytcin release from posterior pituitary
Which pituitary hormone is tonically suppressed by the hypothalamus?
What is the mechanism of suppresion?
Prolactin is tonically suppressed by dopamine
- All other pituitary hormones are stimulated by the hypothalamus
- => If the pituitary stalk is severed, prolactin levels will increase and all other hormone levels will decrease