Intro to Endo Hormones [TRH] Flashcards
(45 cards)
What is endocrinology?
study of hormones secreted by endocrine glands, tissues and cells
What are the 3 types of hormones?
- peptide protein
- lipid
- non-peptide amino acid based
What is the cirulatory half life of hormones determined by?
metabolic modifications of the free (unbounded) hormone into inactive products by the liver and kidney
name 5 key facts about hormones and receptor interactions?
- free hormone binds free R to form complexes
- H-R binding is reversible
- R’s are saturable
- both H & R have varying levels of specificity
- H-R binding activates 2nd messengers +/- transcription in target cells
How is hormone activity terminated in the target cell?
H-R membrane complexes are endocytosed & degraded by proteosome and/or lysosome
What is the hierarchy of the endocrine system?
- hypothalamus
- pituitary gland
+/- 3rd endocrine gland
What are the releasing hormones secreted by the hypothalamus?
What are the inhibitory H’s secreted by the hypothalamus?
releasing:
- GnRH
- CRH
- TRH
- GHRH
inhibitory:
- somatostatin
- dopamine
what are the 2 major fxns of the hypothalamus?
- integrator of homeostatic & reproductive signals
- H secretion that regul8s ant. pituitary prodxn & secretion
(some neurons of hypoT extend into post. pit to release H there too)
name the parts of the pituitary gland?
HOw does the hypoT control the post. pit?
What is the advantage of this?
hypoT neurons extend into the post. pit and produce/release oxytocin & ADH
- H’s are released into post. pit & immediately enter general circulation
***advantage: target cells see stimulatory H very fast!!
Describe the basic outline/pathway of H travel thru the Hypophyseal portal system [ant. pit]
HypoT secrete H [releasing or inhibitory] into hypoT-hypophyseal portal system
- portals bathe ant. pit cells w/ H –> binds
- ant. pit cells release their H’s –> act on 3rd endocrine gland [this doesnt always happen]
- 3rd endo H acts on target cells
What is the MC method of regulating H secretion?
What is the other RARE method?
Negative feedback: MC
-limits amt of H released
POsitive feedback: rare
-reinforcing “snowball’ effect–> more H secreted!
How are peptide H’s usually produced [in what form]?
usually produced as a proH–>needs to be cleaved/activated
ex: proinsulin–> insulin & C-peptide
other ex’s: TSH, LH, FSH
What are 2 types of lipid derived H’s?
- Eicosanoids [PGE]
- Steroid H’s [estrogen]
What 3 subclasses of H’s are formed from amino-acid derived H’s?
- thyroid H’s [T4]
- Catecholamines [Epi]
- tryptophan derivitives [melatonin]
How are steroid H’s synthesized & secreted?
How do steroid H’s traverse cell membranes?
Derived from cholesterol [lipid]–>NOT H20 soluble
- enzyme in SER & golgi convert to final product
- produced & secreted W/O storage!
- bound to carrier/transport proteins in serum
- free H [released from carrier] enters target cell
**they get thru cell membranes via moving down their [] gradients
What is significantly unique about Eicosanoid H’s?
What 3 classes of enzymes produce eicosanoid H’s?
*They are biologically active lipid mediators*
enzymes:
- COx-1 & 2–> PG’s & TXA’s
- Lipoxygenase–> LTE’s
- cypP450 mono-oxygenases–> epoxides
Where do eicosanoids tend to work?
tend to occur @ low levels & work locally
and signal thru GPCR [transmembrane]
***note: they are drug targets!!!
Catecholamines are synthesized and stored how?
which other class of H’s are they most similar to?
**similar to protein H –> bind GPCR
synth/store:
- prduced in neurons
- pkged in vesicles for release on demand
Thyroid H’s are synthesized and stored how?
Which other class of H’s are they most similar to?
**similar to steroids–> bind R’s of nuclear superfamily
Synth/store:
- synth on protein backbone
- processed in lysosomes
- produxn is controlled by enzyme activity and Iodine availability
- secretion is based on diffusion down [] gradient
What downregulates H signaling [general]?
2 main ones
- decrease R #
- increase degradation of H in cells
What upregulates H’s [general]?
2 main things
- increase R #
- decrease degradation of H in cells
Protein H’s bind what type of R?
Protein H’s bind protein R’s on th target cell membrane [cuz cant go thru em]
- R may be tyrosine kinase–> signals passed via phosphorylation cascade
- protein H-R binding may activate 1+ 2nd messenger signaling network
- Gproteins, adenylate cyclase, IP3, Ca/calmodulin etc.
3 ways Gproteins transduce signal cascades
- stimulate adenylate cyclase –> makes cAMP
- increase cytoplasmic Ca++ (released from intracellular stores)
- activate PLC –>makes DAG & IP3
- DAG–> induces PKC activity
- IP3–> induces Ca++ release from ER
