In complete androgen insensitivity syndrome, what is the typical phenotype?

• A. Phenotypically female
• B. Phenotypically male
• C. Ambiguous
• D. Normal male

Answer: (A)

The main idea is how androgen signaling shapes sex development. In complete androgen insensitivity syndrome, the body cannot respond to androgens due to a faulty androgen receptor. Because the tissues don’t react to testosterone or DHT, male internal structures don’t form, and MIS from Sertoli cells eliminates the Müllerian structures, so there’s no uterus or fallopian tubes. With no androgen action to masculinize the genitalia, the external genitalia develop along the female line. At puberty, estrogen produced by aromatization of testosterone drives breast development, but menstruation doesn’t occur because there is no uterus. The overall result is a phenotypically female individual with typically undescended testes.