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Foundation Sciences · Embryology
External Genitalia Development
External genitalia develop from a common indifferent precursor; dihydrotestosterone (DHT) drives masculinisation.
📌 Learning Objectives
- Describe the underlying mechanism of External Genitalia Development.
- Identify the key clinical features and complications of External Genitalia Development.
- Outline the appropriate investigations and management of External Genitalia Development.
- Discuss the implications for patients and families of External Genitalia Development.
📋 Overview
The genital tubercle, urogenital folds and labioscrotal swellings form penis/clitoris, ventral penile shaft/labia minora and scrotum/labia majora respectively. 5α-reductase converts testosterone to DHT.
🔬 Basic Science
The genital tubercle, urogenital folds and labioscrotal swellings form penis/clitoris, ventral penile shaft/labia minora and scrotum/labia majora respectively. 5α-reductase converts testosterone to DHT.
🏥 Clinical Relevance
Congenital adrenal hyperplasia from 21-hydroxylase deficiency virilises XX foetuses.
🧪 Investigations
Investigation depends on clinical context: relevant blood tests, imaging, and specific genetic or histopathological tests as appropriate. Refer to specialist services where indicated.
💊 Management
Management is condition-specific and typically multidisciplinary, combining medical therapy, surgical intervention where appropriate, supportive care, and family/genetic counselling.
Revision Resources – expand the sections below for high-yield notes, exam pearls, key facts and further reading.
MLA High-Yield Notes & Quick Revision ⌄
Common SBA themes: recognising the underlying mechanism, identifying classic clinical features, and choosing the first-line investigation or management step. Watch for inheritance pattern and characteristic associations.
external genitalia
dht
hypospadias
epispadias
ambiguous genitalia
- DHT (via 5α-reductase) drives external male genitalia development.
- The genital tubercle forms the glans penis or glans clitoris.
- Hypospadias results from incomplete fusion of urethral folds (ventral urethral opening).
- Epispadias is associated with bladder exstrophy.
- Ambiguous genitalia in a neonate is a paediatric endocrine emergency.
Exam Pearls ⌄
⭐ High Yield
DHT (via 5α-reductase) drives external male genitalia development.
The genital tubercle forms the glans penis or glans clitoris.
Hypospadias results from incomplete fusion of urethral folds (ventral urethral opening).
Epispadias is associated with bladder exstrophy.
Ambiguous genitalia in a neonate is a paediatric endocrine emergency.
💡 Clinical Pearl
External Genitalia: Congenital adrenal hyperplasia from 21-hydroxylase deficiency virilises XX foetuses.
⚠️ Exam Tip — Common Mistakes
Confusing the mechanism of External Genitalia Development with related conditions.
Missing classic clinical features of External Genitalia Development in SBA stems.
Failing to consider External Genitalia Development in the differential diagnosis.
Key Facts ⌄
DHT (via 5α-reductase) drives external male genitalia development.
The genital tubercle forms the glans penis or glans clitoris.
Hypospadias results from incomplete fusion of urethral folds (ventral urethral opening).
Epispadias is associated with bladder exstrophy.
Ambiguous genitalia in a neonate is a paediatric endocrine emergency.
Related Topics ⌄
References ⌄
- GMC MLA Content Map
- NICE Clinical Knowledge Summaries
- BMJ Best Practice
Further Resources
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