DIP Episode 434 - USMLE Step 2/3 Rapid Review Series 90

Source / episode info

**Episode:**434
**Title:**Divine Intervention Episode 434: USMLE Step 2/3 Rapid Review Series 90
**Published:**2023-01-10
Source:Episode page

One-liner

This episode reviews critical board concepts including the pathophysiology of secondary adrenal insufficiency following chronic steroid use, differentiating between Gilbert's syndrome and G6PD deficiency using characteristic blood smear findings, and identifying various causes and mechanisms of gynecomastia.

High-yield summary

Adrenal Insufficiency (AI): Chronic exogenous glucocorticoid use suppresses the HPA axis (low ACTH/Cortisol). Acute stress reveals this relative insufficiency; lack of response to pressors confirms AI due to cortisol's permissive effect on the sympathetic nervous system. Crucially, secondary AI primarily affects cortisol and is usually associated with preserved aldosterone levels, meaning hyperkalemia is not expected.
Gilbert's Syndrome: Characterized by indirect hyperbilirubinemia due to reduced baseline activity of UDP-glucuronosyltransferase (UGT), exacerbated by metabolic stress. It is benign and requires no treatment.
G6PD Deficiency: Causes acute hemolytic episodes triggered by oxidative stress (e.g., infections). Leads to increased indirect bilirubin and characteristic findings: Heinz bodies and bite cells. The presence of these findings rules out Gilbert's syndrome.
Gynecomastia Etiology: Can result from anti-androgen drugs (Spironolactone, Naltrexone analogs), estrogen excess (liver failure/alcoholism), or low androgen production (e.g., certain antifungals).

Learning objectives

Differentiate the pathophysiology and clinical presentation of secondary adrenal insufficiency versus primary adrenal insufficiency, noting that RAAS/aldosterone is typically preserved in SAI.
Recognize the characteristic hematological findings associated with G6PD deficiency during acute hemolytic episodes (Heinz bodies, bite cells).
Distinguish between Gilbert's syndrome and other causes of indirect hyperbilirubinemia by recognizing the specific blood smear findings indicative of oxidative stress hemolysis.
Identify drugs that induce gynecomastia via anti-androgen effects or estrogen metabolism disruption.
Understand the role of metabolic/oxidative stress in triggering underlying deficiencies (HPA axis, G6PD).

Board exam buzzwords

Condition	Key Finding	Association	Board Exam Tip
Adrenal Insufficiency (AI)	Hypotension unresponsive to pressors	Chronic steroid use; Acute illness/Stress	Always suspect AI if a patient on steroids becomes critically ill and is hypotensive.
G6PD Deficiency	Heinz bodies, bite cells	Oxidative stress (Infection); Hemolysis	The presence of these specific findings rules out Gilbert's syndrome.
Gilbert's Syndrome	Indirect hyperbilirubinemia	Metabolic stress; Reduced UGT activity	Remember: it is benign and not treated.
Gynecomastia	Breast enlargement in males	Anti-androgen drugs (Spironolactone); Estrogen excess (Alcohol)	Think of the mechanism: either blocking androgens or increasing estrogen levels.