A 16-year-old girl with Turner syndrome (45,X) has elevated FSH, streak gonads, and primary amenorrhea. The gonadal failure is caused by:

• A Absent migration of primordial germ cells from yolk sac to genital ridge
• B Accelerated follicular atresia — normal germ cell migration occurs but follicles degenerate postnatally without two intact X chromosomes for oocyte survival ✓
• C Androgen insensitivity of gonadal stromal cells
• D Structural absence of Müllerian ducts preventing ovarian development

Explanation

In Turner syndrome (45,X), germ cells do migrate normally to the gonadal ridge during embryogenesis and follicular development is initiated. However, by birth, accelerated follicular atresia reduces the oocyte pool dramatically; by puberty, the gonads are replaced by fibrous 'streak gonads.' Two intact X chromosomes are required for oocyte survival beyond the primary oocyte stage — the second X contains genes (including those on the inactive X that escape inactivation) needed for follicular maintenance. Müllerian structures (uterus, fallopian tubes) are present in Turner syndrome.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.