ANSWER 11
The symptoms and signs of proximal myopathy, striae and truncal obesity are features of
Cushing’s syndrome. The hyperglycaemia and hypokalaemia would fit this diagnosis. In
addition psychiatric disturbances, typically depression, may occur in Cushing’s syndrome.
Cushing’s disease is due to a pituitary adenoma secreting adrenocorticotrophic hormone
(ACTH). The term ‘Cushing’s syndrome’ is a wider one, and encompasses a group of dis-
orders due to overproduction of cortisol.
- ACTH secretion by a basophil adenoma of the anterior pituitary gland (Cushing’s
disease). - Ectopic ACTH secretion, e.g. from a bronchial carcinoma, often causing a massive
release of cortisol and a severe and rapid onset of symptoms. - Primary adenoma/carcinoma of the adrenal cortex (suppressed ACTH).
- Iatrogenic: corticosteroid treatment. This is the commonest cause in day-to-day
clinical practice.
! Causes of Cushing’s syndrome
This patient’s primary presenting complaint is rapid-onset obesity. The principal causes of
obesity are:
- genetic
- environmental: excessive food intake, lack of exercise
- hormonal: hypothyroidism, Cushing’s syndrome, polycystic ovaries and hyper-
prolactinaemia - alcohol-induced pseudo-Cushing’s syndrome.
This patient should be investigated by an endocrinologist. The first point is to establish is
that this man has abnormal cortisol secretion. There should be loss of the normal diurnal
rhythm with an elevated midnight cortisol level or increased urinary conjugated cortisol
excretion. A dexamethasone suppression test would normally suppress cortisol excretion.
It is then important to exclude common causes of abnormal cortisol excretion such as
stress/depression or alcohol abuse. Measurement of ACTH levels distinguishes between
adrenal (low ACTH) and pituitary/ectopic causes (high ACTH). This patient drinks alcohol
moderately and has a normal gamma-glutamyl transpeptidase. His depression seems to be
a consequence of his cortisol excess rather than a cause, as he has no psychiatric history.
He is having problems with stairs and his social circumstances need to be considered, but
his mobility should improve with appropriate treatment.
His ACTH level is elevated. Bronchial carcinoma is a possibility as he is a heavy smoker
and the onset of his Cushing’s syndrome has been rapid. However his chest X-ray is nor-
mal. In this man a magnetic resonance imaging (MRI) scan (T 1 -weighted coronal image)
through the pituitary shows a hypointense microadenoma (Fig. 11.1, arrow). This can be
treated with surgery or radiotherapy.