Week 9 -Endo Flashcards
What are each of these hormones made from:
Peptide?
Steroids?
Amines?
peptides- amino acids
steroids- cholesterol
amines- tyrosine
What are steroid hormones synthesized and secreted by?
- adrenal cortex
- gonads
- corpus luteum
- placenta
What are the steroid hormones?
- cortisol
- aldosterone
- estradiol and estriol
- progesterone
- testosterone
- 1,25-dihydroxycholecalciferol
What are the amine hormones?
- catecholamines (epi, norepi, dopamine)
- thyroid hormones
Define long loop feedback inhibition.
the hormone feeds all the way back to inhibit the hypothalamus
What is the pituitary gland aka?
the hypophysis
What functions does the anterior pituitary carry out?
The posterior pituitary?
- anterior: endocrine function
- posterior: neurologic function
What connects the pituitary gland to the hypothalamus?
the infundibulum
What does the posterior pituitary secrete?
- ADH
2. oxytocin
What does the anterior pituitary secrete?
- TSH (thyroid stimulating hormone)
- FSH (follicle stimulating hormone)
- LH (lutenizing hormone)
- GH (growth hormone)
- prolactin
- ACTH (adrenocorticotropic hormone)
Why is the blood supply to the hypothalamus unique?
most of the blood supply is venous, supplied by long and short hypophysial portal vessels
What cell type secretes TSH?
Where are they located?
- thyrotrophs
- the anterior pituitary
What cell type secretes FSH?
Where are they located?
- gonadotrophs (also makes LH)
- the anterior pituitary
What cell type secretes LH?
Where are they located?
- gonadotrophs (also makes FSH)
- the anterior pituitary
What cell type secretes ACTH?
Where are they located?
- corticotrophs
- the anterior pituitary
What cell type secretes growth hormone?
Where are they located?
- somatotrophs
- the anterior pituitary
What cell type secretes prolactin?
Where are they located?
- lactotrophs
- the anterior pituitary
What is unique about the secretory pattern of growth hormone?
secretion occurs in a pulsatile pattern, especially during sleep
What are potent stimulators for growth hormone secretion?
hypoglycemia and starvation
What molecule stimulates release of growth hormone?
GHRH (growth hormone releasing hormone)
What molecule inhibits release of growth hormone?
What is it released by?
How does it work?
- somatostatin
- the hypothalamus and pancreas delta cells
- acts by blocking the action of GHRH on the somatotroph
Why is prolactin usually inactive in non-lactating individuals?
prolactin secretion is tonically inhibited by dopamine from the hypothalamus, which overrides the stimulatory effect of TRH/PRH
How does prolactin participate in negative feedback?
it inhibits its own secretion by increasing synthesis/secretion of dopamine from the hypothalamus
What is the major hormone concerned with regulation of body fluid osmolarity?
ADH
What is ADH aka?
vasopressin
What stimulates release of ADH?
Where does it act?
What does it do?
- an increase in serum osmolarity sensed by osmoreceptors in the anterior hypothalamus
- distal tubules of the kidney
- increases water absorption
What does the adrenal medulla secrete?
catecholamines epinephrine (80%) and norepinephrine (20%)
What is each zone of the adrenal cortex called?
What does each layer make?
- zona glomerulosa, mineralocorticoids
- zona fasciculata, glucocorticoids
- zona reticularis, sex hormones (androgens)
What is the basis for the specialization of the layers of the adrenal cortex?
the presence or absence of the enzymes that catalyze various modifications of the steroid nucleus
What is the precursor molecule for all things made in the adrenal cortex?
cholesterol
What is a primary endocrine disorder a problem with?
secretion by the target gland
What is a secondary endocrine disorder a problem with?
secretion by the pituitary gland
What is a tertiary endocrine disorder a problem with?
secretion by the hypothalamus
What is the metabolic clearance rate of a hormone?
the volume of plasma cleared of a hormone per minute
How can hormones be removed from plasma?
- metabolism or binding in the tissues
- hepatic excretion
- renal excretion
What is the relative time of onset of action for protein-bound hormones?
What is their relative length of action?
- slower onset
- longer duration of action
Peptide hormones:
Onset fast or slow?
Duration long or short?
Method of action?
- fast
- short
- surface binding to activate second messengers or ion channels
Steroid/thyroid hormones:
Onset fast or slow?
Duration long or short?
Method of action?
- slow
- long
- alter gene transcription or translation
What class of hormones does the anterior pituitary secrete- peptide, steroid, or amine?
peptide
What molecule stimulates the release of TSH?
Any notable negative control?
- TRH (thyrotropin-releasing hormone)
- none
What molecule stimulates the release of ACTH?
Any notable negative control?
- CRH (corticotropin-releasing hormone)
- none
What molecule stimulates the release of FSH?
Any notable negative control?
- GnRH (gonadotropin-releasing hormone)
- none
What molecule stimulates the release of LH?
Any notable negative control?
- GnRH (gonadotropin-releasing hormone)
- none
What molecule stimulates the release of GH?
Any notable negative control?
- GHRH (growth hormone-releasing hormone) (dominant)
- somatostatin
What molecule stimulates the release of prolactin?
Any notable negative control?
- PRH and TSH, but not really
- dopamine/PIF (dominant)
What is dopamine aka?
PIF (prolactin inhibiting factor)
What pattern of release do all hypothalamic-pituitary axis hormones exhibit?
pulsatile release superimposed on a circadian rhythm
What are the effects of GH?
- most important endocrine regulator of final body size by stimulating linear growth through stimulation if IGF-1 secretion
- opposes the effects of insulin by causing lipolysis in adipose, reducing glucose uptake in muscle, and stimulating gluconeogenesis in the liver
When is the largest release of GH?
What are some other triggers for release?
- during the first 2 hours of deep sleep
2. stress, hypoglycemia, starvation
What is the largest source of plasma IGF-1?
the liver
How is GH secretion turned off?
negative feedback from IGF-1
Why is binding hormones to proteins a good thing?
- increases the half life of the hormone
2. provides a stable reservoir in the blood
What is the primary hormone that controls water balance in the body?
ADH
What causes release of ADH?
How much of a change is needed to produce release of ADH?
What receptor does each use?
- changes in body fluid osmolarity, V2 receptors; increase of only 1%
- drops in blood volume, V1 receptors; drop in 15%
How does ADH respond to a drop in blood volume?
V1 receptors caused generalized arteriolar vasoconstriction in vascular smooth muscle
What are the major functions of oxytocin?
- uterine contraction
- milk let-down
- promotion of maternal behavior
What do thyroid follicles contain?
What, then, is that?
What is it produced by?
- thyroid colloid
- a protein-rich extracellular material
- by follicular cells, endocrine cells around each follicle
What is the major protein in thyroid colloid?
What does it contain as part of its primary structure?
- thyroglobulin
- T3 and T4
What must happen before thyroid hormone can be secreted into the blood?
follicular cells must uptake and hydrolyze the thyroglobulin-linked T3 and T4 to free them
What are the steps in thyroid hormone synthesis?
- iodine trapping by follicular cells
- thyroglobulin made in follicular cells and secreted into the colloid, and iodonation
- conjugation of 2 iodinated tyrosyl gropus to make T3/T4 linked to thyroglobulin
- endocytosis back into the follicular cells, hydrolysis of the T3/T4-thyroglobulin to make free T3/4, as well as DIT and MIT (incomplete molecules that are recycled)
- T3/4 secreted