Antidiuretic hormone disorders

Question 1

Define diabetes insipidus?

Answer 1

Where large amounts of diluted urine are produced which causes extreme thirst.

Question 2

What are the two types of diabetes insipidus and what each type means?

Answer 2

Cranial and nephrogenic.
Cranial where body doesn’t produce enough vasopressin in hypothalamus and thus not enough is stored in pituitary gland.
Nephrogenic diabetes where kidneys does not respond to vasopressin.

Question 3

How can desmopressin be used to diagnose which type of diabetes insipid patient has ?

Answer 3

If patient responds well to desmopressin then it would indicate that they have cranial diabetes insipidus. If they do not respond to it then nephrogenic.

Question 4

What drug can be used in nehprogenic diabetes insipidus and why ?

Answer 4

thiazide diuretics as they produce paradoxical effects

Question 5

What is the difference between vasopressin and desmopressin ?

Answer 5

desmopressin is a more potent analogue of vasopressin, has longer duration of action and no vasoconstrictor effects

Question 6

What is important side effect of desmopresisn?

Answer 6

hyponatraemic convulsions.

Water intoxication where the blood is too diluted and leads to hyponatraemia.

Question 7

What patient counselling should you provide regarding desmopressin ?

Answer 7

Should inform the patients to avoid fluid overload including during swimming and to stop taking during an episode of vomiting and diarrhoea until fluid balance is normal.

Question 8

If a patient is prescribed desmopressin and tricyclic antidepressants what concerns would this raise ?

Answer 8

There is an increased risk of hyponatraemia since tricilycic antidepressants increases secretion of vasopressin

Question 9

Why syndrome of inappropriate antidiuretic hormone secretion is a problem ?

Answer 9

Because body makes too much of a antidiuretic hormone leading to hyponatraemia, body is retaining too much water and diluting concentration of sodium in your blood

Question 10

How can syndrome of inappropriate antidiuretic hormone secretion be treated ?

Answer 10

restriction of fluid or if this not working then demeclocycline which blocks renal tubular effect of ADH or tolvaptan which is vasopressin antagonist.

Question 11

Why hyponatraemia should not be corrected too rapidly ?

Answer 11

because can cause osmotic demyelination of neurones; serious CNS effects

Question 12

Which drugs can cause hyponatraemia?

Answer 12

SSRIs; especially citalopram
haloperidol, phenothiazines
thiazides and thiazide like diuretics
carbamazepine