What is the pathophysiology of cryptorchidism?

Updated: Dec 17, 2020
  • Author: Joel M Sumfest, MD; Chief Editor: Edward David Kim, MD, FACS  more...
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Normal testicular development begins at conception. The testis-determining factor is now identified as the SRY gene (sex-determining region on Y chromosome). The presence of this gene and an intact downstream pathway generally result in testicular formation.

At 3-5 weeks' gestation, the gonadal ridge or indifferent gonad develops, and, at 6 weeks' gestation, primordial germ cell migration occurs. Soon after, Sertoli cells develop and secrete müllerian-inhibiting substance (MIS), the level of which remains high throughout gestation and causes regression of müllerian ducts. At 9 weeks' gestation, Leydig cells develop and secrete testosterone.

Prenatal ultrasonography shows no testicular descent before 28 weeks' gestation, other than transabdominal movement to the internal inguinal ring. Transinguinal migration, thought to be under hormonal control, occurs at 28-40 weeks' gestation, usually resulting in a scrotal testis by the end of a full term of gestation.

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