QuestionSBA
QuestionChoice
No, this is not the correct answer. Cortisol is normally secreted from the zona fasiculata of the adrenal cortex, not from the pituitary gland. A pituitary adenoma would secrete ACTH, rather than cortisol.
10007821
b
Benign pituitary adenoma secreting cortisol
QuestionChoice
The patient demonstrates symptoms of Cushing's syndrome. The investigation results are key in identifying the underlying diagnosis. A combination of raised ACTH and a normal (suppression present) dexamethasone suppression test points towards a pituitary pathology generating excess ACTH. This is also known as Cushing's disease.

The ACTH levels are increased due to increased ACTH secretion from the anterior pituitary gland, which leads to more cortisol secretion from the adrenal cortex. The high-dose dexamethasone suppression test shows cortisol suppression is present, which indicates that the increased ACTH levels are due to secretions from the pituitary gland rather than another ectopic source. This is because dexamethasone exerts negative feedback upon ACTH release from the pituitary gland, but not upon an ectopic source of ACTH.
10007820
a
Benign pituitary adenoma secreting ACTH
QuestionChoice
No, this is not the correct answer. In an adrenal adenoma, there are increased levels of cortisol secretion into the bloodstream from the adrenal cortex. The ACTH levels would be reduced due to the increased negative feedback that high levels of cortisol exert on the anterior pituitary gland to reduce the ACTH levels in the bloodstream.
10007823
d
Excess cortisol secreted by an adrenal adenoma
QuestionChoice
No, this is not the correct answer. When performing a high dose dexamethasone suppression test, cortisol suppression would not be present in a paraneoplastic small cell lung cancer. This is because dexamethasone is a synthetic steroid which acts upon the anterior pituitary to reduce ACTH secretions and subsequent cortisol production through negative feedback mechanisms. By contrast, in ectopic secretion of ACTH from the cells of a lung tumour, there is no negative feedback system being initiated on the cells of the tumour, and so there would be no suppression by dexamethasone.
10007822
c
Paraneoplastic small cell lung cancer
QuestionChoice
No, this is not the correct answer. This would lead to a reduced ACTH levels, due to increased negative feedback on the anterior pituitary gland.
10007824
e
Chronic exposure to prescribed corticosteroids
Concept
Chapter
2693
3764
Cushing's syndrome
Topic
133
Endocrinology
14111
A 58-year-old man presents to the endocrinology clinic complaining of severe fatigue and acute weight gain. On examination, the patient has increased abdominal obesity with purple striae and a dorso-cervical fat pad. It is suspected that he has a condition associated with an excess of cortisol. Investigation results show the following: Cortisol: 1535 nmol/L (reference range = 150-700 nmol/L) ACTH: 120 ng/L (reference range = 10-80 ng/L) High dose dexamethasone suppression test: Cortisol Suppression Present 

Which of the following is the most likely underlying diagnosis?
a