Biochemistry

Question 1

how are sodium and water controlled

Answer 1

Mineralocorticoid activity [sodium]

ADH release and action [water]

Question 2

how is sodium controlled by mineralocorticoid activity

Answer 2

sodium retention in exchange for potassium and/or hydrogen ions

Question 3

what happens if there is too much mineralocorticoid activity

Answer 3

sodium retention

Question 4

what happens if there is too little mineralocorticoid activity

Answer 4

sodium loss

Question 5

what does sodium loss result in

Answer 5

water loss

Question 6

what is the main mineralocorticoid that influences sodium

Answer 6

aldosterone

Question 7

what effects does an increase in ADH cause

Answer 7

concentrated urine

[high urine osmolality]

Question 8

what affect does a decrease in ADH cause

Answer 8

dilutes urine

[low urine osmolality]

Question 9

how does ADH work

Answer 9

acts on the renal tubules to cause water reabsorption

Question 10

what can decreased sodium be due to

Answer 10

SIADH [too much water, decreased secretion]

Addison’s disease [increased sodium loss via adrenal insufficiency]

Question 11

what can increased sodium be due to

Answer 11

diabetes insipidus [increase water loss]

decreased water intake

Question 12

what blood results are seen in addison’s

Answer 12

low sodium

high potassium

Question 13

what non-osmotic stimuli can cause the release of ADH

Answer 13

Hypovolaemia/hypotension
Pain
Nausea/vomiting

Question 14

Tx for too little sodium

Answer 14

give sodium

Question 15

Tx for too much water

Answer 15

fluid restrict

Question 16

Tx for too little water

Answer 16

give water

Question 17

Tx for too much sodium

Answer 17

get rid of excess sodium (and water with it) e.g. diuretics

Question 18

what are the 2 most important factors that determine potassium excretion

Answer 18

GFR

plasma potassium concentration

Question 19

what ECG changes are seen in hyperkalaemia

Answer 19

tall tented T waves

widen of the QRS complexes

Question 20

what are Sx of hyperkalaemia

Answer 20

cardiac arrest
muscle weakness
paraesthesia

Question 21

what are the 3 categories of causes of hyperkalaemia

Answer 21

increased intake
redistribution
decreased excretion

Question 22

what are causes of decreased excretion leading to hyperkalaemia

Answer 22

renal failure
- reduced GFR seen

hypoaldosteronism
- deficiency of aldosterone results in loss of sodium, decreased GFR with retention of potassium and hydrogen

Question 23

what is the role of aldosterone in potassium absorption

Answer 23

stimulates sodium reabsorption at the expense of potassium and hydrogen

Question 24

when is hyperkalaemia cause by hypoaldosteronism often seen

Answer 24

with the use of ACEi and ARB to treat HTN

Question 25

what are causes of redistribution out of cells leading to hyperkalaemia

Answer 25

potassium release from damaged cells - rhabdomyolysis, trauma metabolic acidosis - has hydrogen ions increase so do potassium ions insulin deficiency - insulin stimulates the uptake of potassium

Question 26

Tx of hyperkalaemia

Answer 26

Calcium gluconate Insulin + glucose Tx underlying cause

Question 27

Sx of hypercalcaemia

Answer 27

Stones = kidney stones Bones = bone pain and fractures Groans = constipation, anorexia, abdo pain, N+V Moans = fatigue, myalgia, proximal muscle weakness, joint pain Psychic Overtones= depression, memory loss, confusion, lethargy, coma

Question 28

what are the commonest causes of hypercalcaemia

Answer 28

primary hyperparathyroidism | hypercalcaemia of malignancy

Question 29

how can you differentiate between cancer and hyperparathyroid as a cause of hypercalcaemia

Answer 29

PTH is high in primary hyperparathyroidism

Question 30

Tx of hypercalcaemia

Answer 30

IV saline | Biphosphonates e.g. pamidtronate

Question 31

what happens in familial hypocalciuric hypercalcaemia

Answer 31

a high calcium level is sense by the parathyroids as normal i.e. have normal levels of PTH

Question 32

how can hypocalciuric hypercalcaemia be differentiate from hyperparathyroidism

Answer 32

urinary calcium excretion is inappropriately low in FHH

Question 33

what are features of adrenal insufficiency

Answer 33

``` lethargy anorexia pigmentation of hands/mouth abdo pain weight loss ```

Question 34

what are features of adrenal insufficiency acute crisis

Answer 34

postural hypotension vomiting nausea dehydration

Question 35

what can cause adrenal insufficiency

Answer 35

TB | Autoimmune i.e. Addison's disease

Question 36

what blood results are seen in Addison's disease

Answer 36

hyponatraemia hyperkaelamia elevated serum urea

Question 37

Ix for Addison's

Answer 37

short ACTH stimulation test/Synacthen test; - ACTH given, which should stimulate the release of cortisol - in Addison's plasma cortisol remains low

Question 38

what is not being made in hypo function of the adrenal cortex

Answer 38

cortisol | aldosterone

Question 39

what test can be done to see if secondary failure of the adrenal cortex is due to pituitary insufficiency

Answer 39

insulin stress test

Question 40

Tx of Addison's

Answer 40

15-25mg hydrocortisone (as cortisol replacement) daily in 2-3 doses. Fludrocortisone as aldosterone replacement