QuestionSBA
QuestionChoice
Cushing's syndrome is characterised by excessive cortisol and typically leads to hypernatraemia rather than hyponatraemia due to sodium retention.
10028068
c
Cushing's syndrome
QuestionChoice
Addison's disease can lead to hyponatraemia by reducing sodium re-absorption in the kidneys. However, the history of smoking and small cell lung cancer makes SIADH a more likely diagnosis.
10028070
e
Addison's Disease
QuestionChoice
SIADH is caused by the excess secretion of antidiuretic hormone (ADH), leading to water retention and dilutional hyponatraemia. In this case, the source is from the paraneoplastic secretion of ADH from a likely underlying small cell lung cancer (SCLC).
10028066
a
Syndrome of Inappropriate ADH (SIADH)
QuestionChoice
Primary hyperaldosteronism is characterised by increased aldosterone production and typically leads to hypernatraemia rather than hyponatraemia due to increased sodium retention by the kidneys.
10028067
b
Primary hyperaldosteronism
QuestionChoice
Diabetes insipidus is caused by inadequate secretion of ADH by the posterior pituitary. It typically causes hypernatraemia due to excessive excretion of dilute urine.
10028069
d
Diabetes insipidus
Concept
Chapter
2693
6033
SIADH
Topic
133
Endocrinology
18011
A 60-year-old man presents to A&E experiencing weakness, confusion and generalised swelling for the past week. He is a smoker and drinks 20 units of alcohol a week.

Physical examination shows he has pitting oedema in his legs.

Blood results show hyponatraemia and a low serum osmolality.

A chest x-ray shows he has a small mass in his lungs.

What is the most likely cause of this patient's hyponatraemia?
a