Endo/Repro - Physiology - Hormones Flashcards
Describe some of the classifications of hormones based on their starting point and mode of travel.
Endocrine cells typically release peptide hormones in response to increased intracellular concentrations of what substance?
Does this increase or decrease protein phosphorylation and microtubule action?
[cAMP] + [Ca2+]
(and the associated fusion of vesicles with the cell membrane);
increase
Peptide hormone -coding mRNA is translated on the ER to ____________ and then processed via signal peptide cleavage in the ER to ____________.
What happens next?
Preprohormones,
prohormones;
post-translational modifications (e.g. phosphorylation, glycosylation) in the Golgi
Where are preprohormones synthesized from mRNA?
Where are prohormones then produced? How?
What happens next?
ER,
signal peptide cleavage;
post-translational modifications and processing in the Golgi
Thyroid hormones are synthesized from what precursors?
Steroid hormones are synthesized from what precursors?
Tyrosine + iodide;
cholesterol
In which glands are steroid hormones stored?
They are not stored in any appreciable quantity.
Which is more common, genetic causes of peptide hormone disorders or steroid hormone disorders?
Steroid hormone disorders
(usually defects in the enzyme pathyway from cholesterol to the specific hormone)
How do most genetic steroid hormone disorders occur?
How do most genetic peptide hormone disorders occur?
Mutations in the enzymes in the synthetic pathways;
mutations in the hormones themselves
__________ hormones are released from cells via exocytosis.
Peptide
What cytoskeletal structures in particular are necessary for peptide hormone secretion (via exocytosis)?
Microtubules,
microfilaments
An increase in what cellular content(s) will cause exocytosis of peptide hormones from endocrine organs?
cAMP,
Ca2+
Peptide hormones are released from endocrine organs directly into:
The interstitial space
How does an increase in intracellular Ca2+ and cAMP cause increased peptide secretion from endocrine cells?
Increased protein phosphorylation and microtubule activation
(Ca2+ also activates myosin light-chain kinase, promoting granule movement)
Describe how intracellular Ca2+ increases peptide hormone exocytosis in endocrine tissues via its interactions with MLCK.
True/False.
Both negative and positive feedback systems are involved in virtually all levels of endocrine cell functions.
True
(i.e. transcription, translation, secretion)
At steady state, what is a hormone’s metabolic clearance rate?
The mass of hormone removed per unit time
/
plasma concentration of the hormone
What is the equation for metabolic clearance rate?
What organs are the main locations of hormone degradation?
Liver;
kidneys
True/False.
Virtually all peptide hormone degradation is via proteolysis.
False.
Example processes include: proteolysis, oxidation, reduction, hydroxylation, decarboxylation, methylation, etc.
In hormone kinetics, what are meant by H, R, and HR?
H - free hormone
R - free receptor
HR - hormone-bound receptor
At equilibrium (in hormone kinetics), KAssoc =
KAssoc = [HR] / [H][R]
(also = 1 / Kdissoc)
In hormone kinetics, what is represented by R0?
Initial receptor capacity
(R + HR)
What is a Scatchard plot?
What shape does it display?
A graph representing the ratio of bound hormone to free hormone;
theoretically, a straight line —
— in practice, an exponential curve
The slope of the line in a Scatchard plot is:
The intercept of the line in a Scatchard plot is:
- KAssociation
(i. e. Kd)
R0 (receptor number)
True/False.
A small amount of membrane receptors can often yield the maximum response offered by a peptide hormonal system.
True.
(Limits are in place as to how high the maximal effect can be.)
Which is limited in effect by receptor number? (I.e. more receptors = more effect)
Which is fully activated at a low receptor occupancy? (I.e. more hormone won’t make a difference)
Steroid hormones;
peptide hormones
Which has spare receptors that aren’t being used, peptide or steroid hormones?
Which is limited by the number of spare receptors that are available for use, peptide or steroid hormones?
Peptide (fully activated system at low hormone-receptor occupancy);
steroid (more receptors = more effect)
List some of the major intracellular secondary messengers induced by hormonal action.
cAMP
cGMP
Ca2+
IP3
diacylglycerol
What might occur if a tissue is chronically overstimulated by hormone input?
Downregulation of receptors
(desensitization)
What intracellular secondary messenger is increased by ANP binding?
cGMP
(via guanylyl cyclase)
What intracellular secondary messenger is increased by nitric oxide binding?
cGMP
(via guanylyl cyclase)
What GPCR increases intracellular cGMP?
What does cGMP then activate?
Guanylyl cyclase;
cGMP-dependent protein kinase
What are the two main ways in which hormone response curves can change?
How does the curve change in either option?
Changes in:
sensitivity (left- or right-shift)
or
maximal responsiveness (shifts Vmax up or down)
What two tests are very sensitive for amounts of hormone?
What is the drawback to these tests?
Radioimmunoassays, ELISA;
both measure antigenic amount of hormone, not necessarily biologically active hormone
Are radioimmunoassay and ELISA testing more likely to underestimate or overestimate biologically active hormone concentrations?
Overestimate
(because it measures non-active with active)
What is the specific drawback of radioimmunoassays in measuring hormone levels?
What test avoids this drawback with no loss in sensitivity?
Radiation;
ELISA
What are the three portions of the adenohypophysis?
Describe where they are.
Pars distalis
Pars tuberalis
Pars intermedia
What are the three portions of the neurohypophysis?
Median eminence
Infundibulum
Pars nervosa
What three portions of the hypothalamus release corticotropic hormones?
The paraventricular nucleus,
medial preoptic nucleus,
and arcuate nucleus
What two portions of the hypothalamus send hormones to the neurohypophysis?
The paraventricular nucleus,
the supraoptic nucleus
What is found within the median eminence of the pituitary?
The neurovascular region connecting the hypothalamus to the adenohypophysis
What type of circulation connects the adenohypophysis to the median eminence?
A portal system
(capillary bed draining into capillary bed)
Describe the hypothalamic-hypophyseal portal system.
List the hormonal release triggered by each of the following:
GnRH
TRH
CRH
GHRH
GnRH: LH, FSH;
TRH: TSH, prolactin;
CRH: ACTH;
GHRH: GH
List the corticotropic hormone that causes the release of each of the following:
LH
GH
Prolactin
TSH
ACTH
FSH
LH: GnRH
GH: GHRH
Prolactin: TRH
TSH: TRH
ACTH: CRH
FSH: GnRH
Release of what hormone(s) of the anterior pituitary is inhibited by somatostatin?
GH;
TSH
Release of what hormone(s) of the anterior pituitary is inhibited by dopamine?
Prolactin
(dopamine also known as prolactin-inhibiting factor)
What are the five cell types of the adenohypophysis (in order of decreasing quantity)?
Somatotrophs
Mammotrophs
Corticotrophs
Gonadotrophs
Thyrotrophs
Cellular differentiation in the anterior pituitary is mediated by what transcription factor?
Pit-1
True/False.
Anterior pituitary secretion is near-continuous to meet the body’s continous basal metabolic needs.
False.
Anterior pituitary secretion is pulsatile.
The pituitary gland sits within what bony structure of the _________ bone?
Sella turcica;
sphenoid
True/False.
The anterior pituitary is derived from the fetal neuroectoderm.
False.
The anterior pituitary is derived from the fetal foregut.
What cell type of the adenohypophysis secretes LH and FSH?
Gonadotrophs
What cell type of the adenohypophysis secretes thyrotropin (TSH)?
Thyrotrophs
What cell type of the adenohypophysis secretes growth hormone and somatotropin?
Somatotrophs
What cell type of the adenohypophysis secretes prolactin?
Mammotrophs
What cell type of the adenohypophysis secretes adrenocorticotropin (ACTH)?
Corticotrophs
What type of cell in the adenohypophysis is most abundant? What proportion does it make up?
What three types of cell are next most abundant?
What type of cell in the adenohypophysis is least abundant?
Somatotrophs (50%)
gonadotrophs, corticotrophs, mammotrophs (15% each)
thyrotrophs (5%)
What substances stimulate ACTH secretion from the adenohypophysis?
What are a few positive modulators for this process?
CRH, ADH;
norepinephrine, acetylcholine, and 5-HT
What substances inhibit ACTH secretion from the adenohypophysis?
What are a few negative modulators for ACTH release?
Cortisol, brain natriuretic peptide;
ACTH, endorphins, GABA
Cortisol inhibits which portions of the hypothalamic-pituitary axis?
CRH and ACTH release
What disease is characterized by primary adrenal insufficiency?
Addison’s disease
CRH and ACTH both increase intracellular levels of what enzyme (leading to all other downstream effects)?
PKA
Growth hormone shares homology with what other pituitary hormone?
Prolactin
True/False.
Most of the cells of the adenohypophysis secrete some level of GH.
True.
Pulsatile ______ increases GH release from the adenohypophysis.
Pulsatile ______ decreases GH release from the adenohypophysis.
______ also decreases GH release from the adenohypophysis.
GHRH;
somatostatin;
IGF-1 (increases somatostatin release)
What is the main effect of growth hormone?
Stimulation of postnatal growth
Prolactin release from the adenohypophysis is mostly stimulated by what substance?
Prolactin release from the adenohypophysis is mostly inhibited by what substance?
TRH;
dopamine (PIF)
Which adenohypophyseal hormones are all members of the glycoprotein hormone family?
FSH, LH, TSH, β-HCG
TSH, LH, FSH, and β-HCG are each made of ___ subunits.
Which gives the specificity?
2;
β
Which hormone produced by the follicular cells of the thyroid inhibits TRH and TSH release?
T3
True/False.
FSH and LH decrease after menopause.
False.
They increase.
Name the precusor to ACTH.
What else does this precursor become?
Proopiomelanocortin;
β-endorphins, α-melanocyte-stimulating hormone
How many pulses of GnRH per hour are required to maintain baseline levels of both LH and FSH?
1 per hour
Less frequent GnRH pulses (1 per 3 hours) stimulates what?
More frequent GnRH pulses stimulates what?
FSH secretion;
LH secretion
What substance selectively inihibits FSH secretion?
Inhibin
LH secretion is mediated by _______ GnRH pulses.
FSH secretion is mediated by _______ GnRH pulses.
Fast;
slow
Name the respective tropic hormone responsible for increasing release of each of the following:
Prolactin
LH
TSH
GH
FSH
ACTH
TRH
GnRH
TRH
GHRH
GnRH
CRH
Name the respective adenohypophyseal hormones released by stimulation from the following tropic hormones:
TRH
GnRH
GHRH
CRH
TSH, prolactin
FSH, LH
GH
ACTH
What transport protein(s) carry oxytocin and ADH from the hypothalamus to the neurohypophysis?
Neurophysin I (oxytocin)
neurophysin II (ADH)
ADH and oxytocin secretion is mainly mediated via:
Neuronal input
Is transport from the hypothalamus to the neurohypophysis slow or fast transport?
Fast
(mm / hour)
True/False.
The paraventricular nucleus produces only oxytocin and the supraoptic nucleus produces only ADH.
False.
The paraventricular nucleus produces mainly oxytocin and the supraoptic nucleus produces mainly ADH, but both produce a small quantity of the alternate hormone.
True/False.
Both the paraventricular and supraoptic nuclei each produce both ADH and oxytocin.
True.
(at least in small amounts)
ADH and oxytocin are released from what portion of the neurohypophysis?
The pars nervosa
What are pituicytes?
Glial cells of the neurohypophysis
Are the axons found in the pars nervosa of the neurohypophysis myelinated or unmyelinated?
Unmyelinated
What are the main functions of ADH?
Increased renal H2O reabsorption;
systemic vasoconstriction (at pharmacological doses)
What are the main functions of oxytocin?
Uterine contraction;
mammary gland myoepithelial contraction;
bonding
ADH and oxytocin are both ___ amino acids in length.
They only differ in ___ amino acid residues.
9;
2
The similarity in structure between ADH and oxytocin means what?
They may have overlapping effects
What are some examples of the types of injury can disrupt the neuronal tracts that transport ADH and oxytocin?
Is regeneration of these axons possible?
Trauma, tumor, surgery;
yes
ADH binds what two receptors?
(What does each do?)
V1 (vasoconstriction)
V2 (vasodilation; renal H2O reabsorption)
What renal effects does ADH cause via the V2 receptor?
1) Reabsorption of NaCl via stimulation of Na/K/2Cl co-transport in the thick ascendening limb
2) Increase the permeability of the collecting duct to urea
3) Increase permeability of the collecting ducts to H2O
What effect does ADH have on cortisol levels?
ADH stimulates release of ACTH
The supraoptic nucleus mainly secretes:
The paraventricular nucleus mainly secretes:
ADH
oxytocin
What is the main stimulus for ADH secretion?
What are two others?
Increased plasma osmolarity
hypovolemia, increased CSF [Na+]
(also, nausea, angiotensin II, temperature increase, nicotene, histamine, bradykinin)
What is the main inhibitory stimulus preventing ADH secretion?
What are two others?
Decreased plasma osmolarity
normo- or hypervolemia, decreased CSF [Na+]
(also, EtOH, ANP, temperature decrease, norepinephrine)
What effect does EtOH ingestion have on ADH secretion?
Inhibition
What are the primary S/Sy of diabetes insipidus?
What are some others?
Polyuria (5-15 L/day), polydipsia;
hypernatremia, increased serum osmolality (290 - 295 mOsm/Kg), muscle weakness, fever, hypoosmotic urine
What are the main electrolyte and osmolality changes seen in diabetes insipidus?
Hypernatremia;
increased serum osmolality (290 - 295 mOsm/Kg)
What are the two types of diabetes insipidus?
Central;
nephrogenic
A patient presents with a 2-week history of polyuria and polydipsia. You suspect diabetes insipidus. This needs to be differentiated from what other potential causes?
Diabetes mellitus,
psychogenic polydipsia/polyuria
What are some potential causes of central diabetes inspidus?
Destruction of hypothalamic nuclei
(tumors, trauma, surgery);
inherited
(neurophysin mutation)
What are some potential causes of nephrogenic diabetes insipidus?
Chronic kidney disease,
ADH receptor or aquaporin2 deficiency,
drugs (lithium)
What test results can be used to diagnose central diabetes insipidus?
Water deprivation test (urine osmolality will not increase);
desmopressin test (urine osmolality will increase)
What is the main therapy for central diabetes insipidus?
Desmopressin
(vasopressin analog)
What are the S/Sy of syndrome of inappropriate antidiuretic hormone secretion (SIADH)?
Most patients have no signs (no peripheral edema, no signs of dehydration);
hyponatremia below 110 mmol/l –> weakness, lethargy (leading to coma)
What are some potential causes of syndrome of inappropriate antidiuretic hormone secretion (SIADH)?
Para-neoplastic syndromes (lungs, pancreas, lymphoma);
non-neoplastic lung disease (COPD, pneumonia, TB);
brain disorders (tumors, encephalitis, meningitis, hemorrhage);
certain drugs (antidepressants, diuretics, narcotics)
Describe the expected lab results in a patient with SIADH.
Hypervolemia,
low Serum osmolality (<270 mOsm/kg),
hyponatremia (<130 mmol/l),
hypertonic urine (>300 mOsm/kg),
increased urine [Na+] (>20mmol/l)
What are the main treatment options for SIADH?
Water restriction;
medications to block V2 receptors
On routine labwork in an asymptomatic patient, you notice that they are hyponatremic and their urine is hypertonic. What do you suspect?
SIADH
Oxytocin causes contraction of smooth muscle in what two locations in particular?
Breast myoepithelial cells;
the uterus
What clinical uses does pitocin (oxytocin) have in the peripartum period?
To induce labor;
to stop uterine bleeding after labor
The actions of oxytocin are augmented by what endogenous substance and blocked by what other endogenous substance?
Estrogen;
catecholamines
Which is involved in the let-down reflex in breastfeeding, oxytocin or prolactin?
Oxytocin
Is milk ejection during breastfeeding by positive or negative pressure or both?
(I.e. does the breast use positive pressure to eject the milk or does the infant create negative pressure and draw it out?)
Positive pressure
(myoepithelial cell contraction in response to suckling)
True/False.
Milk ejection from the breast is psychogenic.
True.