Hutson John M, Hasthorpe Suzanne
Douglas Stephens Laboratory, Murdoch Childrens Research Institute, Melbourne, Victoria, Australia.
Cell Tissue Res. 2005 Oct;322(1):155-8. doi: 10.1007/s00441-005-1126-4. Epub 2005 Nov 3.
Testicular descent occurs in two stages. The transabdominal phase (8-15 weeks) is controlled by enlargement of the caudal genito-inguinal ligament (gubernaculum) and regression of the cranial ligament. Insulin-like 3 from the Leydig cell appears to be the prime stimulator of gubernacular growth, augmented by Müllerian inhibiting substance/anti-Müllerian hormone. Testosterone causes regression of the cranial ligament. The inguinoscrotal phase (25-35 weeks) requires the migration of the gubernaculum from the groin to the scrotum; this migration is guided by the genito-femoral nerve releasing calcitonin gene-related peptide under the influence of androgen. The neonatal gonocyte transforms into a type A spermatogonium at 3-12 months of age, a step that is now known to be crucial for subsequent fertility, as the stem cells for spermatogenesis are created in this structure. This step is blocked in undescended testis and, hence, orchidopexy is currently recommended at 6-12 months of age. Congenital cryptorchidism is caused by the failure of gubernacular migration to the scrotum (1%-2%) but we now recognise that another 1%-2% of boys have acquired cryptorchidism, secondary to the failure of spermatic cord elongation with growth of the boy. These latter cases come to operation at 5-10 years of age. Surgery remains the mainstay of treatment, as hormonal therapy has not been proven to be effective, presumably because testicular descent is a complex anatomical mechanism.
睾丸下降分两个阶段。经腹阶段（8 - 15周）受尾侧生殖腹股沟韧带（睾丸引带）增大及头侧韧带退化的控制。来自睾丸间质细胞的胰岛素样3似乎是睾丸引带生长的主要刺激物，苗勒管抑制物质/抗苗勒管激素可增强其作用。睾酮导致头侧韧带退化。腹股沟阴囊阶段（25 - 35周）需要睾丸引带从腹股沟迁移至阴囊；这种迁移受生殖股神经引导，在雄激素影响下释放降钙素基因相关肽。新生儿生殖母细胞在3 - 12个月大时转变为A型精原细胞，现在已知这一步骤对后续生育至关重要，因为精子发生的干细胞在此结构中产生。这一步骤在隐睾中受阻，因此，目前建议在6 - 12个月大时进行睾丸固定术。先天性隐睾是由睾丸引带向阴囊迁移失败所致（1% - 2%），但我们现在认识到另有1% - 2%的男孩患有后天性隐睾，继发于精索随着男孩生长而伸长失败。这些后者的病例在5 - 10岁时进行手术。手术仍然是主要的治疗方法，因为激素治疗尚未被证明有效，可能是因为睾丸下降是一个复杂的解剖学机制。
