Lalloo, 50 years old, a chronic smoker, presents with history of hemoptysis. He was having truncal obesity and hypeension. He had an elevated ACTH level which was not suppressive with high dose dexamethasone. What would be the most probable diagnosis
**Core Concept**
Lalloo's presentation with hemoptysis, truncal obesity, hypertension, and an elevated ACTH level that is not suppressive with high-dose dexamethasone suggests an endocrine disorder involving the hypothalamic-pituitary-adrenal (HPA) axis. The primary issue here is the non-suppressive nature of ACTH, indicating autonomous cortisol production.
**Why the Correct Answer is Right**
The elevated ACTH level that is not suppressive with high-dose dexamethasone points towards an ectopic ACTH-producing tumor or a Cushing's syndrome due to a pituitary adenoma. However, given Lalloo's truncal obesity, hypertension, and hemoptysis, an ectopic source is more likely. The absence of suppression with high-dose dexamethasone is a hallmark of ectopic ACTH syndrome. This is because ectopic ACTH-producing tumors do not have a feedback mechanism to suppress ACTH production in response to glucocorticoid administration.
**Why Each Wrong Option is Incorrect**
* **Option A:** Cushing's disease due to a pituitary adenoma is less likely due to the presence of hemoptysis and truncal obesity, which are more suggestive of an ectopic source.
* **Option B:** Adrenal carcinoma is a possibility but the non-suppressive nature of ACTH with high-dose dexamethasone makes it less likely.
* **Option D:** Ectopic ACTH-producing tumor is the most likely diagnosis given the clinical presentation and the non-suppressive nature of ACTH.
**Clinical Pearl / High-Yield Fact**
The presence of truncal obesity and hypertension in a patient with hemoptysis and an elevated ACTH level that is not suppressive with high-dose dexamethasone should raise suspicion for an ectopic ACTH-producing tumor. This is a classic presentation of ectopic ACTH syndrome, which is often associated with small cell lung carcinoma.
**Correct Answer:** C.