Diagnosis of Cushingoid Features with Low ACTH
The patient presents with symptoms like obesity, moon facies, abdominal striae, and hypertension, which are characteristic of Cushing's syndrome (excess cortisol).
Analysis of Test Results
- Overnight Dexamethasone Suppression Test (ON DST): Serum cortisol is greater than 50 nmol/L. This indicates a failure to suppress cortisol production, confirming hypercortisolism.
- Serum ACTH Level: Serum ACTH is less than 1.1 pmol/L. This is a critical finding, indicating that the ACTH production from the pituitary gland is suppressed.
- Imaging Studies: Both adrenal imaging and brain CT/MRI are unremarkable. This rules out significant adrenal tumors (adenoma/carcinoma) or pituitary tumors (Cushing's disease) as the cause.
Reasoning for Diagnosis
- Low ACTH levels (< 1.1 pmol/L) exclude pituitary causes (Cushing's disease) and ectopic ACTH production, as these conditions typically result in normal or high ACTH levels.
- The suppression of ACTH suggests that the negative feedback mechanism of the HPA axis is intact but overridden, most commonly by exogenous glucocorticoid administration.
- The patient's known history of rheumatoid arthritis increases the likelihood of long-term treatment with glucocorticoids (like prednisone or dexamethasone), a common therapy for RA.
- Therefore, the combination of Cushingoid symptoms, cortisol non-suppression, suppressed ACTH, normal imaging, and a history suggestive of steroid use strongly points towards exogenous glucocorticoid use.
The diagnosis is concluded to be exogenous glucocorticoid use because it is the most common cause of ACTH suppression in the context of Cushingoid symptoms when pituitary and adrenal sources have been ruled out by imaging.
Important Questions from Adrenal Disorders
- Which one of the following is a cause of Secondary Hyperaldosteronism?
Which of the following are correct regarding Cortisol?
1. Levels are highest in the morning on waking.
2. Cortisol falls dramatically during an illness.
3. More than 95% circulating cortisol is protein bound.
4. It is the major glucocorticoid in humans and can also activate mineralocorticoid receptors.
Select the answer using the code given below :
- Hirsutism is seen in which of the following ?
1. Polycystic ovarian syndrome
2. Congenital adrenal hyperplasia
3. Hypothyroidism
4. Ovarian tumour
Select the correct answer using the code given below: - A patient presents with circulatory shock, nausea, vomiting and diarrhoea. A diagnosis of acute adrenal crisis is considered. A blood sample is stored for measurement of serum cortisol and treatment started without delay. Which of the following are appropriate interventions?
1. IV normal saline
2. IV hydrocortisone 100 mg stat
3. IV 10% glucose
4. IV KCl as infusion
Select the correct answer using the code given below: - Escape behaviour with paroxysmal occurrence is seen in:
