Examkin

Question

Difficulty: MediumOrdering Laboratory Tests

For each of the following endocrine and neuroendocrine clinical scenarios, select the most appropriate targeted laboratory investigation to confirm the suspected underlying diagnosis.

  • A 42-year-old female presenting with episodic facial flushing, chronic watery diarrhea, and a new-onset right-sided heart murmur.24-hour urine 5-hydroxyindoleacetic acid (5-HIAA)
  • A 38-year-old male evaluated for recurrent calcium oxalate nephrolithiasis, dyspepsia refractory to proton pump inhibitors, and persistent hypercalcemia.Serum intact parathyroid hormone and gastrin levels
  • A 48-year-old female experiencing paroxysmal severe headaches, unexplained diaphoresis, palpitations, and episodic severe hypertension.Plasma fractionated free metanephrines
  • A 45-year-old male presenting with progressive proximal muscle weakness, easy bruising, wide violaceous abdominal striae, and unexplained hypokalemia.Overnight 1-mg dexamethasone suppression test

Answer

The presentations map to diagnostic tests for Carcinoid syndrome (5-HIAA), Multiple Endocrine Neoplasia type 1 (PTH and gastrin), Pheochromocytoma (metanephrines), and Cushing's syndrome (dexamethasone suppression test), respectively.
Each scenario describes a classic presentation of a functional neuroendocrine or endocrine tumor. The foundational principle in working up these conditions is that biochemical confirmation of hormone excess must be established through highly specific and sensitive laboratory testing prior to localizing the tumor with imaging.

Step-by-Step Solution

1
Analyze the first clinical scenario for hallmark neuroendocrine signs.
Identify flushing, diarrhea, and valvular disease as carcinoid syndrome.
Recognizing the carcinoid triad directs testing toward serotonin overproduction.
2
Evaluate the second scenario for syndromic associations.
Identify hypercalcemia and refractory ulcers as probable MEN1 (hyperparathyroidism and gastrinoma).
Clustering of endocrine abnormalities requires testing multiple specific hormone axes simultaneously.
3
Assess the third scenario for catecholamine excess.
Identify the classic triad of headache, sweating, and tachycardia as pheochromocytoma.
Suspicion of pheochromocytoma requires high-sensitivity biochemical screening before any imaging is attempted.
4
Examine the fourth scenario for signs of hypercortisolism.
Identify proximal weakness, striae, bruising, and hypokalemia as Cushing's syndrome.
Clinical stigmata of Cushing's require demonstration of autonomous cortisol secretion.

Key Concept

Selecting the appropriate initial biochemical screening test for suspected endocrine and neuroendocrine tumors based on classic clinical syndromes.
Rate this question

Topics

Ordering Laboratory Tests

More questions from this topic