CHAPTER 9 Cryptorchidism: Diagnosis and Management
What is the SRY gene, what does it do, and where is it located?
SRY stands for Sex determining Region on the Y chromosome. It is located on the short arm of the Y chromosome.
What role does SRY play in testis development?
SRY is believed to induce Sertoli cell differentiation and testis development. SRY upregulates the expression of SOX9 gene, which then promotes further differentiation of Sertoli cells.
What role does SOX9 play in testis development?
The SOX9 gene is structurally similar to SRY. SOX9 is probably activated by SRY because both genes are expressed by fetal Sertoli cells. SOX9 is believed to (1) further promote the differentiation of the Sertoli cells, and (2) upregulate mullerian-inhibiting substance (MIS) gene expression.
During sexual differentiation of the gonad into a testis, what are the first cells to differentiate in the testis and approximately when does that happen?
The Sertoli cells differentiate at around 6 to 8 weeks.
What is the primordial hormone of the fetal testis? When and where does it begin to get produced?
Mullerian-inhibiting substance (MIS) is a glycoprotein that is produced and secreted by Sertoli cells around the 8th week of gestation and is responsible for regression of the mullerian ducts. Evidence for the role of MIS in testicular descent is conflicting.
What 2 structures are the remnants of the regressed mullerian ducts?
The appendix testis and the prostatic utricle.
What cells in the testes are responsible for the production of testosterone in utero?
Leydig cells, just like in adults.
Describe the 2 separate stages of testicular descent. Describe the role and actions for insulin-like hormone 3 and calcitonin gene-related peptide. Where are these substances made?
1. The first stage occurs at 8 to 15 weeks gestation. There is enlargement of the gubernaculum and regression of the cranial suspensory ligament (CSL). Leydig cells produce insulin-like hormone 3, which stimulates the caudal gubernaculums to grow and become thicker. Mullerian-inhibiting substance may have a role in stimulating the swelling reaction in the gubernaculum.
2. The second stage occurs between 25 and 35 weeks gestation and requires the migration of the gubernaculum and testis from the inguinal region to the scrotum. This stage is thought to be more androgen dependent. In addition, the genitofemoral nerve releases calcitonin gene-related peptide, which may guide the migration of the testis.
What is the CSL and what happens to it in adults?
The undifferentiated gonad is initially located high in the abdomen, anchored by the CSL. During intraabdominal descent (1st stage of testicular descent), androgens lead to the regression of the CSL. In females, the CSL persists because of the absence of androgens.
When does testicular descent typically begin and finish?
Descent typically begins in the 23rd week of gestation when the processus vaginalis elongates into the scrotum. At 24 weeks, descent is complete in 10% of fetuses, at 27 weeks 50%, at 28 weeks 75%, and at 34 weeks 80%.
True/False: Spontaneous descent of an undescended testicle is rare after the first year of life.
True. Less than 10% of cryptorchid testes will descend spontaneously beyond 6 months of age.
What are the incidences of cryptorchidism in premature, full-term neonates, 1-year olds, and adults, respectively?
The incidences are 30%, 3%, 1%, and 1%, respectively.
At 1 year of age, what percentage of cryptorchid testes have descended in premature infants and in full-term infants, respectively?
It is 95% for premature infants and 75% for full-term infants. The majority of all descents will have occurred in the first 3 to 6 months of life.
What is now believed to be the single greatest predisposing factor for cryptorchidism?
Low birth weight (independent of length of gestation).
What maternal factors contribute to cryptorchidism?
Endocrine disrupting chemicals (EDC) found in many pesticides have been shown to have antiandrogenic effects on the developing male fetus in both human and animal models. This is thought to cause genital malformations including cryptorchidism, hypospadias, and micropenis. Paternal exposure to EDCs may also be associated with increased risk for cryptorchidism.
What is the relationship between maternal smoking and obesity on the incidence of cryptorchidism?
Maternal smoking and obesity are not associated with increased incidence of cryptorchidism.
What percentage of cryptorchid testes are bilateral?
30%.
What percentage of cases of cryptorchidism are accompanied by epididymal anomalies?
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