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Difficulty: MediumEndocrinology and Metabolism

Match each suspected endocrine disorder with the most appropriate confirmatory dynamic diagnostic test used to definitively establish the diagnosis.

  • Suspected acromegalyOral glucose tolerance test with growth hormone measurement
  • Suspected primary adrenal insufficiencyHigh-dose synthetic ACTH (cosyntropin) stimulation test
  • Suspected hypercortisolism (Cushing syndrome)Low-dose dexamethasone suppression test
  • Suspected diabetes insipidusWater deprivation test followed by desmopressin administration

Answer

Acromegaly pairs with the oral glucose tolerance test; Primary adrenal insufficiency pairs with the high-dose synthetic ACTH stimulation test; Hypercortisolism pairs with the low-dose dexamethasone suppression test; Diabetes insipidus pairs with the water deprivation test.
The correct pairings rely on the fundamental rule of endocrinology: hypofunctioning glands are evaluated with stimulation tests (e.g., cosyntropin for adrenals, water deprivation for ADH), while hyperfunctioning states are evaluated with suppression tests (e.g., glucose for growth hormone, dexamethasone for cortisol).

Step-by-Step Solution

1
Analyze the underlying pathophysiology of each condition to determine if it is a disorder of hormone excess or hormone deficiency.
Acromegaly and hypercortisolism are states of excess; adrenal insufficiency and diabetes insipidus are states of deficiency.
General endocrine principles dictate that states of suspected hormone excess are evaluated with suppression tests, whereas states of suspected deficiency are evaluated with stimulation tests.
2
Identify the appropriate suppression tests for the hypersecreting conditions.
Glucose normally suppresses Growth Hormone, making the oral glucose tolerance test ideal for acromegaly. Dexamethasone normally suppresses ACTH and cortisol, making the low-dose dexamethasone suppression test ideal for hypercortisolism.
Confirming autonomy of hypersecreting tumors requires proving resistance to normal negative physiological feedback.
3
Identify the appropriate stimulation tests for the hyposecreting conditions.
Exogenous ACTH (cosyntropin) directly stimulates the adrenal gland, testing reserve in adrenal insufficiency. Water deprivation tests the endogenous ADH reserve, and desmopressin tests renal responsiveness.
Confirming a deficient state requires challenging the target organ to produce a response to its primary trophic hormone or physiological trigger.

Key Concept

Endocrine dynamic testing principles
Estimated Time:1m 0s
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Topics

Endocrinology and Metabolism

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