Biochemistry and Date handling

Question 1

sudden onset polyuria and polydipsia after severe headache?

Answer 1

diabetes insipidus

Question 2

when does frequent drinking become abnormal?

Answer 2

e.g needing to get up during the night, cant go anywhere without a bottle of water, drinking 10-11 L of water a day`

Question 3

signs that polyuria is abnormal?

Answer 3

if not drinking but still urinating a lot

older man with prostate problems

Question 4

what is the normal urine output?

Answer 4

1-2L per 24 hrs

polyuria = >3L

Question 5

name 6 groups of causes of polydipsia/polyuria?

Answer 5

neurogenic
nephrogenic
iatrogenic
metabolic
psychiatric
other

Question 6

what investigations may be useful in polyuria and polydipsia?

Answer 6

Us&Es
glucose
calcium
urine
serum osmolality

Question 7

low urine osmolality + high urea?

Answer 7

high urea indicates dehydration
low urine osmolality = failure to retain water
most likely diagnosis = diabetes insipidus

Question 8

test for diabetes insipidus?

Answer 8

water deprivation test

Question 9

how do you calculate serum osmolality?

Answer 9

2[Na + K] + glucose + urea

Question 10

what is normal serum osmolality?

Answer 10

275-295mosm/kg

Question 11

clinical signs of dehydration?

Answer 11

dry skin
dry mucous membranes
skin not as tight
generally look unwell
low JVP
drop in erect blood pressure

Question 12

what must be considered in water deprivation test?

Answer 12

must not be steroid or thyroid deficit as test will be uninterpretable

Question 13

how does water deprivation test determine whether diabetes insipidus is cranial or nephrogenic?

Answer 13

give DDAVP
if condition improves = cranial
if condition unchanged = nephrogenic

Question 14

what can cause high prolactin?

Answer 14

tonically inhibited
drugs
something blocking the inhibitory pathway - eg. tumours

Question 15

what further examinations may be done in suspected diabetes insipidus due to pituitary hypofunction?

Answer 15

fundoscopy - check optic disc and visual fields

MRI of brain

Question 16

how is pituitary hypofunction/diabetes insipidus managed?

Answer 16

hormone replacement
- levothyroxine
- hydrocortisone
- testosterone
surgery if tumour

Question 17

what can indicate abnormal pigmentation/tanning?

Answer 17

in non sun-exposed sites
if not exposed to sun
in hand creases
in sites of trauma/scars
in buccal mucosa
melanoma moles etc

Question 18

biochemical features of addisons disease?

Answer 18

low Na+
high K+
high urea
high creatinine

Question 19

causes of addisons?

Answer 19

autoimmune
iatrogenic
TB
cancers
ischaemia

Question 20

first test for addisons?

Answer 20

synachthen test (SST)
- differentiates whether cranial or adrenal problem

Question 21

when is synacthen test best performed and when is the test avoided?

Answer 21

early morning (9am)
avoid in asthma and pregnancy and post pituitary surgery

Question 22

further investigations in addisons after synacthen?

Answer 22

plasma ACTH
adrenals Abs
imaging

Question 23

what causes increased tanning in addisons?

Answer 23

precursor of ACTH produced in excess to try and overcome lack of cortisol
same precursor for ACTH and MSH so results in increased ACTH and MSH

Question 24

how is addisons disease managed?

Answer 24

oral hydrocortisone, split dosing
consider fludricortisone
sick day rules

Question 25

low sodium, high potassium, high urea?

Answer 25

addisons

Question 26

high Na+, low K+, normal urea?

Answer 26

conns syndrome

Question 27

low Na+, low K+, Low urea?

Answer 27

SIADH

Question 28

management for Conns syndrome?

Answer 28

spironolactone

Question 29

what can cause SIADH?

Answer 29

cancer
lung disease
CNS
drugs

Question 30

how is SIADH managed?

Answer 30

treat underlying cause
fluid restriction
demeclocycline
tolyaptran

Question 31

what is demeclocycline?

Answer 31

an antibiotic but reduced responsiveness of collecting tubules to ADH

Question 32

what is tolyaptran?

Answer 32

vasopressor receptor agonist

Question 33

what are the features of an Addisonian crisis?

Answer 33

shock
tachycardia
low BP
pigmented
high blood glucose
ketones +ve
high urea and creatinine
low Na+
High bicarbonate (doesn't fit with DKA)

Question 34

investigations and management in Addisonian crisis?

Answer 34

check random cortisol (don’t wait for result)
IV hydrocortisone
IV N. saline
IV sliding scale insulin