The question of when “men’s testicles drop” refers to a process that takes place primarily during the development of the male fetus, not in adolescence or adulthood. Testicular descent is a complex, hormonally-driven migration that moves the testes from their initial location inside the abdomen to their final position within the scrotum. The entire process of normal descent is largely completed before birth, specifically during the third trimester of pregnancy.
The Normal Timeline of Testicular Descent
Testicular descent is a two-phase process beginning early in gestation, driven by different hormonal signals. The first phase, called the transabdominal phase, occurs between 8 and 15 weeks of gestation. During this stage, the testes move to the area near the internal inguinal ring, largely regulated by the hormone Insulin-like Factor 3 (INSL3) produced by the fetal Leydig cells.
The second phase, the inguinoscrotal phase, is responsible for the final movement through the inguinal canal into the scrotum. This stage is primarily androgen-dependent, relying on testosterone and its derivatives. This final descent typically takes place between 25 and 35 weeks of gestation, meaning most full-term infants have fully descended testes at birth. The gubernaculum, a cord-like structure, guides the testes along the path to the scrotum.
In a small percentage of full-term infants, the testes may not have completed their journey by the time of delivery. In these cases, spontaneous descent often occurs shortly after birth, usually within the first three to six months of life. This postnatal descent is facilitated by a surge in luteinizing hormone (LH) and testosterone that naturally occurs in the first few months of life. If the testes have not descended by six months of age, spontaneous resolution is considered unlikely, and medical intervention is typically considered.
Why Testicles Must Descend
The primary reason testicles must descend outside the body cavity is the need for a cooler environment for sperm production, a process called spermatogenesis. Normal core body temperature, which is approximately 37°C (98.6°F), is too high to support the healthy development of mature sperm. The scrotal position allows the testes to maintain a temperature that is usually 2 to 3°C lower than the rest of the body.
This lower temperature is achieved through the testes’ external location and the action of muscles like the cremaster, which raises and lowers the testes to help regulate temperature. The descended position ensures the developing male will have the physiological conditions necessary for healthy sperm production later in life. Failure to achieve this cooler external environment can lead to germ cell damage and impaired fertility potential.
When Descent Fails: Understanding Cryptorchidism
Cryptorchidism, commonly known as undescended testicles (UDT), is the failure of one or both testicles to complete their journey into the scrotum. This is the most common birth defect of the male genital tract, affecting about 3% of full-term male infants and significantly more premature infants. While the testes are usually found along the normal path of descent, they can sometimes be ectopic, meaning they have deviated to an abnormal location.
A separate condition, the retractile testis, is often mistaken for true cryptorchidism but does not require intervention. A retractile testis can be manually brought down into the scrotum during an examination and will remain there for a time, due to a hyperactive cremasteric reflex. A true undescended testis, however, cannot be easily manipulated into the scrotum or will immediately retract back into the inguinal canal or abdomen.
The diagnosis of cryptorchidism is typically made shortly after birth during a physical examination. The condition is monitored over the first few months of life, as a significant number of testes will descend spontaneously. If the testis has not descended by six months of age, it is considered unlikely to do so, and the risk of germ cell damage begins to increase.
Treatment Options and Long-Term Considerations
Once a testis remains undescended past six months of age, medical intervention is recommended to mitigate the long-term risks. The current consensus is that the optimal window for treatment is between six and twelve months of age. The standard treatment is a surgical procedure called orchiopexy, where the surgeon carefully brings the testis down into the scrotum and secures it in place.
Orchiopexy is a highly effective, typically outpatient procedure that involves a small incision in the groin and sometimes the scrotum. Hormonal therapy, such as the use of human chorionic gonadotropin (hCG), is rarely used as a primary treatment because its success rates are low. The procedure should be performed early because the longer the testis remains in the warmer, non-scrotal environment, the greater the potential for germ cell damage.
Untreated cryptorchidism significantly increases the risk of two major long-term health concerns. The first is an elevated risk of male infertility, particularly if both testes were undescended. The second is an increased risk of developing testicular cancer later in life, though this risk is reduced by performing orchiopexy before puberty.