Antidiuretic Hormone Disorders

Question 1

What are the two types of diabetes insipidus?

Answer 1

Pituitary (cranial) and nephrogenic.

Question 2

What is pituitary (cranial) diabetes insipidus?

Answer 2

Diabetes insipidus caused by insufficient levels of ADH.

Question 3

What is nephrogenic diabetes insipidus?

Answer 3

Diabetes insipidus caused by kidney defects.

Question 4

What are the symptoms of diabetes insipidus?

Answer 4

Severe thirst, frequent urination, bed-wetting, trouble sleeping, fussiness in children, fever, vomiting, diarrhoea, delayed growth, weight loss.

Question 5

What drugs are used in the treatment of pituitary diabetes insipidus?

Answer 5

Vasopressin (antidiuretic hormone (ADH)) and its analogue, desmopressin.

Question 6

How are doses of vasopressin and desmopressin tailored in the treatment of diabetes insipidus?

Answer 6

Doses are tailored to produce slight diuresis every 24 hours to avoid water intoxication.

Question 7

What is the difference between desmopressin and vasopressin with regards to clinical effects?

Answer 7

Desmopressin is more potent and has a longer duration of action than vasopressin.

Question 8

How is desmopressin used in the differential diagnosis of diabetes insipidus?

Answer 8

Failure to respond to a dose of desmopressin suggests nephrogenic diabetes insipidus.

Question 9

Both pituitary and nephrogenic diabetes insipidus can benefit from the paradoxical antidiuretic effect of which drugs?

Answer 9

Thiazide diuretics.

Question 10

How can use of carbamazepine be useful in the treatment of diabetes insipidus?

Answer 10

It is sometimes useful in the sensitization of renal tubules to the action of remaining vasopressin.

Question 11

Give some other uses of desmopressin, other than in the treatment of diabetes insipidus.

Answer 11

In haemophilia and Von Willebrand’s disease to boost factor 8 concentration. It can also be used in the treatment of nocturnal enuresis.

Question 12

Give some other uses of vasopressin, other than in the treatment of diabetes insipidus.

Answer 12

Vasopressin can be used to control variceal bleeding in portal hypertension, due to its vasoconstrictor properties.

Question 13

How should patients taking desmopressin manage their fluid intake?

Answer 13

Patients should limit fluid intake to a minimum from one hour before dose until eight hours afterwards.

Question 14

Why should intranasal desmopressin not be given for the treatment of nocturnal enuresis?

Answer 14

There is an increased risk of hyponatraemic convulsions.

Question 15

What are some of the common side effects associated with desmopressin use?

Answer 15

Fluid retention, hyponatraemia on administration without limiting fluid dose (with convulsions in more serious cases), stomach pain, headache, nausea, vomiting.

Question 16

How can the risk of hyponatraemic convulsions when using desmopressin be reduced?

Answer 16

It can be minimised by avoiding fluid overload and stopping the medication during vomiting or diarrhoea until fluid balance back to normal. Keeping to the recommended dose. Avoiding drugs which increase secretion of vasopressin.

Question 17

Give some drugs which increase the secretion of vasopressin.

Answer 17

Paracetamol, nicotine, TCAs.

Question 18

There is an increased risk of hyponatraemic convulsions when using desmopressin in the elderly. How should these patients be monitored?

Answer 18

Measure baseline serum sodium concentration, then monitor regularly during treatment. Discontinue of levels fall below baseline.

Question 19

What effect does desmopressin use have in pregnancy?

Answer 19

A small oxytocic effect in the third trimester, leading to an increased risk of pre-eclampsia.