Hormone Action II Flashcards
what is the “master control center” of the endocrine system?
why is this the case?
the hypothalamus
is the integration of the nervous system + endocrine system
what is the target organ of the hypothalamus?
the pituitary gland
discuss the chemical structure of hypothalmic hormones.
why is this important?
- N - terminus: is cyclic: this bulkiness protects hypothalmic hormones (which are small) from degradation in the blood
- C - terminus: is an amide group that links a hormone specific peptide chain through its carbonyl. as a result, there is no “free” COOH group
both of these features extend the half life of hypothalmic hormones
hypothalmic hormones bind to:
- what receptors?
- inducing an intracellar response in what way?
- GCPRs (Gq) on the ant pituitary (adenohypophysis)
- Gq –> PLC –> IP3 + DAG –> increasing Ca++ and PKC
- this stimulates exocytosis of pre-existing vesicles into blood stream
list the ant pituitary (adenohypophysis) hormones released by the following hypothalmic hormones:
- TRH
- PRF
- PIH
- CRH
- GnRH
- GHRH
- Somatostatin
- thyrotropin releasing hormone –> TSH (+ prolactin?)
- prolactin stimulating hormone –> prolactin
- prolacting nhibiting hormone (dopamine) –> inhibits prolactin release
- corticotropoic releasing hormone –> ACTH
- gonadotropin releasing hormone –> LH & FSH
- growth hormone releasing hormone –> GH
- somatostatin –> inhibitrs GH release
whwat are the six hormones released by the ant pituitary (adenohypophysis) and where do they each act?
acidophiles = lactotrophes (prolactin) & somatotrophes (GH)
basophiles = corticotrophes (ACTH), gonadotrophes (LH & FSH) & thyrotrophes (TSH)
which pituitary hormones act on the JAK-STAT receptor?
what chemical structure category do these hormones fit into?
both are proteins
- GH
- prolactin
induces dimerization –> JAK-P - intracellular chain-P - STAT recruitement - STAT-P (by JAK)
which pituitary hormones act on the Gs receptor?
what chemical structure categorization do these hormones they fall into? describe their structure.
- TSH
- FSH
- LH
- all are glycoproteins made of alpha-beta dimer:
- a subunits are the same for all three each hormones
- b subunits have the unique. hormone-dependent aa sequence
- what is POMC?
- where is it produced?
- what is its purpose?
- pro-opiomelanocortin
- produce in ant pituitary (adenohypophysis) & intermediate pituitary
- serves as a precursor hormone for:
- ACTH
- MSH
- lipotropin
- endodorphins
pro-opiomelanocortin (POMC) is a precursor for which hormones?
breifly, what do each of these horones do?
- ACTH: made in response to CRH, acts on adrenal cortex to induce glucocorticoid synthesis
- MSH (melanin stimulating hormone): stimulates melanin synthesis in skin
- endorophin: decrease pain reception causing euphoria
- lipotropin
POMC processing involves
- what modifications?
- at what sequences?
- based on?
- glycosylations + acetylations + extensive proteolytic cleavage
- basic protein sequences
- POMC cleavages (and product produced) based on proteolytic activity expressed by the ant pituitary cell type receiving it
the posterior pituitary (neurophysis) produces what hormones?
what do these hormones have in common?
what are their individual roles?
- technically does not produce any hormones
-
stores two hormones produced by hypothalmic neurons:
- which are:
- oxytocin - stimulates lactation and uterine contraction (during delivery)
- vasopressin (ADH) - regulate body osmolarity
- both:
- are cyclic nonaptides
- are bound by neurophysins (carrier proteins) in the blood
- which are:
what are neurophysins?
carrier proteins that associated with oxytocin and vasopressin (ADH)
how would a dietary deficiency of iodide affect the thyroid hormone cascade?
- would decrease production of T3 & T4 which would
- increase production of TRH (hypothalamus)
- increase production of TSH (anteiror pituitary)
(negative feedback)
discuss the steps & molecules involved in iodide oxidation
- iodide taken up into folliclular cell cytoplasm using a Na/K ATPase
- iodide oxidaized to iodine to thyroperoxidase
- iodine secreted into lumen, then added to tyrosine residues on thyroglobulin
after thyroglobulin gets iodinated - what steps occur next in the synthesis of thyroid hormones?
- ionization of residues forms DIT and MIT molecules (DIT = two Is on a tyrosine residue, MIT = one I on a tyrosine residue)
- ionidonated thyroglobulin is stored in the colloid until TSH stimulates follicular cells to:
- uptake colloid to bring along iodinated thyroglobulin, which becomes fused to vesicles
- lysosomes degrade the iodonated thyroglobulin to release T3 (MID + DIT) and T4 (DIT + DIT)
is T3 or T4 more active?
T3
how are T4 and T3 transported to target tissues & why is this significant?
what kind of receptors do they bind to?
describe this binding.
- T3 and T4 are thyroid hormones and thus lipophillic
- they require protein carriers - thyroxin binding globulin (TBG) and thyroxin binding pre-albumin (TPBA) which will
- increase their half life by 99%
- then drop them off at their receptors, which are
- nuclear receptors (subclass II)
- binding is “non-covalent”
- if T4 (less active thyroid hormone) is bound, it will be converted to T3 by a deiodinase
- nuclear receptors (subclass II)
- they require protein carriers - thyroxin binding globulin (TBG) and thyroxin binding pre-albumin (TPBA) which will
what is the role of diodinase and where is it found?
- found in target tissues of thyroid hormones
- convert T4 to T3 (more active form)
what is rT3?
the inactive form of thyroid hormones
what are the means by which thyroid hormones inactivated?
- conversion of T4 –> rT3
- glucaronidation
- de - ionidation / carboxylation / amination
