QuestionSBA
QuestionChoice
Diabetes insipidus is characterised by loss of ADH function resulting in polyuria, polydipsia, and hypernatraemia. Serum osmolality is typically raised (>300), whilst urine osmolality is decreased (<300). Diabetes insipidus may have a cranial cause (lack of ADH release), or a nephrogenic cause (resistance to ADH action).
10006876
a
Diabetes insipidus
QuestionChoice
SIADH would cause hyponatraemia, and is a known complication of small-cell lung cancer. This is caused by excess ADH release resulting in increased reabsorption of water in the nephron and a decrease in blood osmolality. The subsequent increase in glomerular filtration rate due to increased blood volume causes reduced aldosterone release, resulting in less sodium reabsorption and increased urine osmolality. SIADH would typically present as a euvolaemic hyponatraemia.
10006877
b
Syndrome of inappropriate ADH secretion (SIADH)
QuestionChoice
Heart failure can result in a hypervolaemic hyponatraemia. In heart failure, decreased cardiac output and blood pressure result in increased release of ADH causing increased water reabsorption.
10006880
e
Heart failure
QuestionChoice
Addison's disease is caused by adrenal insufficiency, and characteristically presents with hyponatraemia and hyperkalaemia. This is due to the decreased aldosterone release by the adrenal cortex, and thus decreased sodium reabsorption in the nephron.
10006879
d
Addison's disease
QuestionChoice
Diarrhoea is a cause of hypovolaemic hyponatraemia. It results in excess sodium and water loss in the GI tract.
10006878
c
Diarrhoea
Concept
Chapter
2693
4014
Hyponatraemia
Topic
170
Clinical Chemistry
13922
A 64-year-old lady who is an inpatient on a respiratory ward for small cell lung carcinoma has been experiencing nausea and headache for the past two days. She has also vomited twice today and is complaining of cramping in her right leg. Blood tests are performed and her serum sodium is found to be reduced at 114 mmol/L (normal range 135-145 mmol/L).

Which of the following is not a cause of hyponatraemia?
a