Hyponatraemia (SIADH) + Diabetes Insipidus Flashcards
What is the difference between osmolality and osmolarity?
- osmolality = solute concentration is osmoles of solute/kg of solution
- osmolarity = solute concentration in osmoles of solute per litre of solution
If there is an increased extracellular (outside the cell) osmolality (high solutes around the cell) which of the following will occur?
1 - H2O enters the cell and cell becomes swollen
1 - H2O leaves the cell and cell becomes dehydrated
1 - H2O moves between intra and extracellular space, but no change to the cell
4 - no change
1 - H2O leaves the cell and cell becomes dehydrated
- H2O leaves to dilute high extracellular solutes
- the cell loses H2O and becomes dehydrated
If there is an increased intracellular (inside the cell) osmolality (high solutes inside the cell) which of the following will occur?
1 - H2O enters the cell and cell becomes swollen
1 - H2O leaves the cell and cell becomes dehydrated
1 - H2O moves between intra and extracellular space, but no change to the cell
4 - no change
1 - H2O enters the cell and cell becomes swollen
- H2O enters the cell to dilute the high intracellular (inside the cell) osmolality
- the cell becomes swollen and oedema occurs
How does the body detect when there is change in the osmolality in the plasma?
1 - juxtaglomerular cells
2 - V2 receptors in collecting tubules
3 - baroreceptors
4 - osmoreceptors in hypothalamus
4 - osmoreceptors in hypothalamus
- located in the anterior hypothalamus on the wall of the 3rd ventricle
If we lose H2O due to sweat or we eat a really salty meal, the extracellular (outside the cell) osmolality (ECO) will increase, stimulating the osmoreceptors located in the anterior wall of the 3rd ventricle and the the anterior hypothalamus. This cluster of nuclei in the hypothalamus is called the supraoptic nuclei. When they detect the increased ECO what happens?
1 - anterior pituitary reduces anti-diuretic hormone secretion to reduce H2O retention
2 - anterior pituitary increase anti-diuretic hormone secretion to increase H2O retention
3 - posterior pituitary reduces anti-diuretic hormone secretion to reduce H2O retention
4 - posterior pituitary increases anti-diuretic hormone secretion to increase H2O retention
4 - posterior pituitary increases anti-diuretic hormone secretion to increase H2O retention
- hypothalamus stimulates the posterior pituitary gland
- posterior pituitary gland releases anti-diuretic hormone (ADH) aka vasopressin
- ADH retains H2O through kidneys and vasoconstricts blood vessels
- the body also instigates thirst to consume more H2O
One of the key functions of anti-diuretic hormone is to retain H2O in the collecting tubules. How is it able to do this?
1 - reabsorbs Na+ and H2O follows
2 - binds AVPR2 in distal convoluted tubules increasing aquaporin-2
3 - increases Na+/Cl-/K+ channels in thick ascending loop of Henley thus increasing their reabsorption
4 - reduces eGFR and therefore less H2O is lost in urine
2 - binds AVPR2 in distal convoluted tubules increasing aquaporin-2
- aquaporin-2 are responsible for reabsorbing just H2O
One of the key functions of anti-diuretic hormone (ADH), aka vasopressin is to retain water in the kidneys. What is one other key function of ADH?
1 - induce vasoconstriction and increase BP
2 - reduce cardia workload
3 - induce vasodilation and reduce BP
4 - retain K+ and Na+ in collecting tubules
1 - induce vasoconstriction and increase BP
What is the normal plasma osmolality range?
1 - 100-200 mosmol/kg
2 - 185-195 mosmol/kg
3 - 275-295 mosmol/kg
4 - 355-395 mosmol/kg
3 - 275-295 mosmol/kg
Formula =
2 x (Na+ K+) + Glucose + Urea
Example using normal values:
- 2 x (Na+ add K+ = 135) = 278 mmol/L
- glucose = 5.5 mmol/L
- urea = 3 mmol/L
- 278 + 8 + 5.5 + 3 = 294.5 mosmol/kg
When extracellular osmolality increases, due to fluid loss, the sensation of thirst is stimulated and there is a release of anti-diuretic hormone (ADH). What 2 parts of the brain are involved in this response?
1 - thalamus
2 - pituitary gland
3 - hypothalamus
4 - cerebral cortex
3 - hypothalamus = ADH
4 - cerebral cortex = thirst
What happens to thirst and anti-diuretic hormone release in the presence of:
- high plasma osmolality (lots of solutes in blood)
- low plasma osmolality (fewer solutes in blood)
- high plasma osmolality = thirst and ADH release
- low plasma osmolality = no thirst and no ADH release
What cation is required for the release of packed anti-diuretic hormone in vesicles to be released into the posterior pituitary gland and then into the blood?
1 - Na+
2 - Ca2+
3 - K+
4 - Mg2+
2 - Ca2+
Which of the following does anti-diuretic hormone NOT have an effect and increase H2O retention? Label the image with the labels below:
1 - proximal tubule
2 - distal tubule
3 - collecting tubule
4 - collecting duct epithelia
1 - proximal tubule
Anti-diuretic hormone (ADH) able to increase water retention in the kidneys. ADH is able to bind with vasopressin receptor 2 (AVPR2). What type of membrane receptor is this and what does this trigger intracellularly?
1 - receptor tyrosine kinase
2 - ion channel receptor
3 - GPCR
4 - enzyme linked receptor
3 - GPCR
- specifically Gas
- increases synthesis of aquaporin 2 (AQP-2)
- vesicles containing AQP-2 bind with the cell membrane
- more AQP-2 increases water retention
What does polyuria mean?
1 - increased urine output
2 - pain when urinating
3 - lack of urine
4 - all of the above
1 - increased urine output
- poly = lots of
- uria = urine
- production of lots of urine
What does polydipsia mean?
1 - increased urine output
2 - pain when urinating
3 - reduced thirst
4 - increased thirst
4 - increased thirst
- poly = lots of
- dipsia = greek for thirst-
What effect does polyuria (high urine output) have on plasma osmolality?
1 - increases plasma osmolality
2 - decreases plasma osmolality
3 - no effect on plasma osmolality
1 - increases plasma osmolality
- less fluid means an increase of solutes in plasma and an increased osmolality
- polydipsia = excessive thirst and water consumption = decrease of plasma osmolality
What effect does polydipsia (high thirst) and increased fluid intake have on plasma osmolality?
1 - increases plasma osmolality
2 - decreases plasma osmolality
3 - no effect on plasma osmolality
2 - decreases plasma osmolality
- more fluid means solutes are diluted, and thus a reduced plasma osmolality
If a patient presents with polyuria and/or polydipsia, what is the first disease that must be ruled out?
1 - CKD
2 - diabetes
3 - liver disease
4 - HF
2 - diabetes
- high solutes (hyperglycaemia or hypercalcaemia) means the body increases ADH and thirst to dilute solutes and reduce osmolality
Diabetes insipidus relates to polyuria, that is tasteless as no sugar like in diabetes mellitus. There are different types of diabetes insipidus. One of these is central diabetes insipidus (CDI), a rare disorder cause polydipsia and polyuria. In CDI, the problem is located centrally. Typically what is the issue in CDI?
1 - increased ADH and larger volumes of H2O retained
2 - increased ADH and less H2O retained
3 - decreased ADH and less H2O retained
4 - decreased ADH and more H2O retained
3 - decreased ADH and less H2O retained
- central problem is in hypothalamus menaing less ADH is released
- less ADH means less retention of H2O and polyuria
- polyuria means higher osmolality and therefore polydipsia to dilute higher osmolality
Central diabetes insipidus (CDI) is a rare disorder that can cause polydipsia and polyuria. Which of the following is NOT typically a cause of CDI?
1 - idiopathic = 27%
2 - head trauma or neurosurgery
3 - genetic (5%)
4 - pituitary tumour (no ADH released)
5 - schizophrenia
5 - schizophrenia
- associated with Dipsogenic diabetes insipidus
- idiopathic is most common = 27%
Central diabetes insipidus (CDI) is a rare disorder that can cause polydipsia and polyuria. This is due to a problem is located centrally in the hypothalamus or pituitary gland reducing anti-diuretic hormone (ADH) release, meaning reduced ADH reduces vasoconstriction of blood vessels and reduced H2O retention in kidneys. How can this be treated?
1 - synthetic ADH called desmopressin is administered
2 - administer spirolactone
3 - provide psychoeducation and CBT
4 - all of the above
1 - synthetic ADH called desmopressin is administered
- can cause hyponatraemia (low Na+) IF the polydipsia is not treated (stop excessive fluid intake)
Nephrogenic diabetes insipidus (NDI) is a rare disorder that can cause polydipsia and polyuria. Typically what is the issue in NDI?
1 - nephrons are inflamed and become blocked so H2O is retained
2 - nephrons are damaged and unresponsive to ADH so more H2O is retained
3 - nephrons are damaged and unresponsive to ADH so H2O is not retained
3 - nephrons are damaged and unresponsive to ADH so H2O is not retained
- less response to ADH means polyuria, causing increased osmolality
- increased osmolality triggers polydipsia to dilute high osmolality
Nephrogenic diabetes insipidus (NDI) is a rare disorder that can cause polydipsia and polyuria as the renal tubules are damaged and become less responsive to ADH. Which of the following is NOT a cause of NDI?
1 - genetic disorder (receptor dysfunction)
2 - medications (lithium)
3 - polycystic kidney disease
4 - increased vassopressinase
5 - persistant hypercalcaemia (Ca2+) and hypokalaemia (K+)
4 - increased vassopressinase
Nephrogenic diabetes insipidus (DI) is a rare disorder that can cause polydipsia and polyuria. Caused by damage to the nephron in the kidneys, which are unresponsive to anti-diuretic hormone (ADH). The most common causes include genetic disorder, medications (lithium) and kidney disease. How can this be treated?
1 - synthetic ADH called desmopressin is administered
2 - administer spirolactone
3 - provide psychoeducation and CBT
4 - address cause of nephron damage
4 - address cause of nephron damage
- correct metabolic or drug cause damaging nephrons
- likely to be due to thiazide diuretics (help clear fluid from the body) / NSAIDs
Dipsogenic diabetes insipidus (DDI) is a rare disorder that can cause polydipsia and polyuria. What is this and what causes this?
1 - mutated ADH that is not effective upon acting on the kidneys
2 - psychological condition causing patient to consume excessive water
3 - nephrons are damaged and unresponsive to ADH
4 - hypothalamus secretes less ADH
2 - psychological condition causing patient to consume excessive water
- high water intake causes reduced osmolality
- patient has less ADH and polyuria in an attempt to increase plasma osmolality
- common in patients with mental disorders such as psychosis