Androgen insensitivity syndrome vs 5-alpha-reductase deficiency
How to tell Androgen insensitivity syndrome and 5-alpha-reductase deficiency apart when a board question makes them look alike.
AIS has androgen receptor resistance with scant hair; 5-alpha-reductase deficiency has low DHT and virilizes at puberty.
Side by side
Androgen insensitivity causes 46,XY phenotypic female with testes, absent uterus, scant pubic hair, and normal or high testosterone due to androgen receptor resistance.
5-alpha-reductase deficiency causes 46,XY undervirilized external genitalia at birth with virilization at puberty because DHT synthesis is impaired.
Androgen insensitivity causes 46,XY phenotypic female with testes, absent uterus, scant pubic hair, and normal or high testosterone due to androgen receptor resistance.
5-alpha-reductase deficiency causes 46,XY undervirilized external genitalia at birth with virilization at puberty because DHT synthesis is impaired.
AIS: 46,XY, high testosterone with high LH and increased estradiol, absent uterus from AMH, scant pubic/axillary hair, and female external phenotype.
5-alpha-reductase deficiency: 46,XY, uterus absent, high testosterone-to-DHT ratio often above 10, undervirilized external genitalia with virilization at puberty.
The trap
AIS is androgen receptor resistance with scant hair and no puberty virilization; 5-alpha-reductase deficiency is DHT defect with puberty virilization.
The repair move
Before naming the answer, force the stem through the separator: AIS is androgen receptor resistance with scant hair and no puberty virilization; 5-alpha-reductase deficiency is DHT defect with puberty virilization.
Try a free question
CoreA 16-year-old phenotypically female adolescent presents with primary amenorrhea. She has Tanner stage 4 breasts, scant pubic and axillary hair, blind-ending vaginal pouch, and absent uterus. Bilateral palpable masses in the inguinal canals are identified as testes. Karyotype is 46,XY. Testosterone is in male range; LH is elevated. Which condition is most likely?
Show answer and explanation
Answer: A. Complete androgen insensitivity syndrome (CAIS). CAIS is X-linked AR gene mutation. Testes secrete AMH (Mullerian regression, NO uterus) and testosterone (which cannot act on tissues with absent AR, so Wolffian ducts regress and external genitalia default to female). Breast development at puberty (testosterone aromatized to estradiol). Scant pubic/axillary hair (androgen-dependent). Manage with orchiectomy after puberty (testicular tumor risk).
Why the other choices are tempting
- B. 5-alpha-reductase deficiency: 46,XY with ambiguous or female-appearing external genitalia at birth, virilizes at puberty (testosterone surge can act on receptors); high testosterone-to-DHT ratio.
- C. Mullerian agenesis (MRKH): 46,XX female with absent uterus/upper vagina but normal female external genitalia, normal pubic hair, normal female karyotype.
- D. Klinefelter: 47,XXY male phenotype with hypogonadism.
- E. Turner: 45,X female phenotype with short stature, streak ovaries, primary amenorrhea, webbed neck.
Flashcards
Tap a card to flip it.
What clue supports Androgen insensitivity syndrome?
Choose Androgen insensitivity syndrome when the stem gives this pattern: Androgen insensitivity causes 46,XY phenotypic female with testes, absent uterus, scant pubic hair, and normal or high testosterone due to androgen receptor resistance.
What clue supports 5-alpha-reductase deficiency?
Choose 5-alpha-reductase deficiency when the stem gives this contrasting pattern: 5-alpha-reductase deficiency causes 46,XY undervirilized external genitalia at birth with virilization at puberty because DHT synthesis is impaired.
Quick answers
What is the fastest way to tell Androgen insensitivity syndrome from 5-alpha-reductase deficiency?
AIS has androgen receptor resistance with scant hair; 5-alpha-reductase deficiency has low DHT and virilizes at puberty.
What is the key clue for Androgen insensitivity syndrome?
Androgen insensitivity causes 46,XY phenotypic female with testes, absent uterus, scant pubic hair, and normal or high testosterone due to androgen receptor resistance.
What is the key clue for 5-alpha-reductase deficiency?
5-alpha-reductase deficiency causes 46,XY undervirilized external genitalia at birth with virilization at puberty because DHT synthesis is impaired.
What is the common trap with Androgen insensitivity syndrome vs 5-alpha-reductase deficiency?
AIS is androgen receptor resistance with scant hair and no puberty virilization; 5-alpha-reductase deficiency is DHT defect with puberty virilization.