CHAPTER 13 Disorders of Sexual Development
What structure undergoes condensation and shortening to promote descent of the testis?
The gubernaculum anchors the testis to the genital region condenses to allow descent.
How many attachments does the gubernaculum have and what are they called?
The gubernaculum typically has 5 attachments, which are called slips.
What transcription factor is associated with testicular descent from the abdominal cavity to the inguinal canal (transabdominal)?
INSL3 (insulin-like 3) is expressed by testicular Leydig cells. Production of this protein rises in the second trimester of gestation and works in conjunction with testosterone to promote testicular descent.
What transcription factor is critical for gonadal differentiation toward the male lineage?
SRY (sex determining region on the short arm of the Y chromosome), also known as the testis determining factor (TDF). SRY directly binds to specific DNA loci and regulates the differentiation of the bipotential gonad toward testicular development. Thus far, the SRY protein is considered the “master switch” that initiates testicular development.
What happens if the TDF is not expressed or mutated in a genotypic male (46 XY)?
The bipotential gonad differentiates toward the ovarian lineage. Sertoli and Leydig cells do not form; Mullerian inhibiting substance (MIS) and testosterone are not produced. Thus, Mullerian duct development is promoted and Wolffian duct development is suppressed.
At what time point in fetal development does the gonad differentiate to become a testis or ovary?
Between the 6th to 8th week of gestation, the indifferent (bipotential) gonad differentiates into either a testis or an ovary.
What cell type is responsible for producing MIS?
The fetal Sertoli cells produce MIS.
What soluble factor superfamily does MIS belong to?
Transforming growth factor beta (TGFβ).
Which active steroid hormone is important for Wolffian duct induction and proliferation?
The presence of testosterone results in the proliferation of the Wolffian duct system and the development of the efferent ductules, rete testis, epididymis, vas deferens, and seminal vesicles.
What enzyme converts testosterone into dihydrotestosterone (DHT)?
The conversion is mediated by 5-alpha-reductase.
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