The idea of testicles continuously “dropping” as a person ages is a common misconception. This belief often confuses the permanent developmental event of descent with daily functional adjustments and the effects of aging. The testicles, or testes, are the two oval-shaped glands housed in the scrotum, suspended outside the body by the spermatic cord. While their permanent anatomical placement is set early in life, the scrotum and its contents undergo significant positional shifts daily, structural changes during puberty, and gradual changes in appearance with advanced age.
The Initial Descent: Fetal Development and Infancy
The true “dropping” of the testicles, known as testicular descent, is a two-stage biological process that concludes before or shortly after birth. The testicles initially form high in the abdominal cavity, similar to the ovaries in a female fetus. The first phase, the transabdominal stage, is regulated by hormones like Insulin-like hormone 3 (Insl3) and involves the development of the gubernaculum, a cord-like structure that anchors the testes near the groin.
The second phase, the inguinoscrotal stage, occurs later in gestation, typically between 25 and 35 weeks, or in the first few months after birth. During this stage, the gubernaculum actively guides the testes through the inguinal canal and into the scrotum. This process is primarily controlled by androgens, such as testosterone, which cause the gubernaculum to regress and the testes to descend. A failure in this developmental process results in cryptorchidism, or undescended testes, which is a condition requiring medical attention.
Changes During Puberty
Puberty marks a period of profound structural change, though the permanent anatomical position of the testes remains fixed. The onset is signaled by a noticeable increase in testicular size, driven by the maturation and growth of the seminiferous tubules, where sperm production begins. Testicular volume continues to increase throughout puberty, reaching adult size around Tanner stage 4.
This growth is fueled by increased levels of Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH), which stimulate the production of sperm and testosterone. The scrotal sac matures; the skin darkens, becomes thinner, and starts to hang lower due to the increased mass and changes in the surrounding tissues. This results in a lower resting position, but it is a structural enlargement, not a continuation of the fetal descent process.
Daily Positional Shifts: Temperature Regulation
The movement observed daily is related to a continuous system of temperature control, not aging or growth. The testicles must maintain a temperature slightly lower than the core body temperature—ideally around 34 degrees Celsius (93.2°F)—for optimal sperm production (spermatogenesis). The scrotum functions as a thermoregulator to maintain this environment.
Two specialized muscles govern these daily positional shifts. The dartos muscle, a layer of smooth muscle beneath the scrotal skin, contracts when cold, causing the scrotum to tighten and pull the testes closer to the body to conserve heat. Conversely, it relaxes in warmer conditions, allowing the scrotum to become looser for heat dissipation. The cremaster muscle, surrounding the spermatic cord, is responsible for the cremasteric reflex, which quickly raises and lowers the testicle in response to cold, physical activity, or arousal.
Structural Changes Associated with Aging
The perception that testicles “drop” with age is primarily due to changes in the surrounding scrotal tissue, not a further internal descent of the testes. Over decades, the skin and underlying support structures lose their firmness and elasticity, a natural part of the aging process. Specifically, the smooth muscle tone of the dartos muscle gradually diminishes, causing the scrotal sac to become looser and more pendulous. This laxity creates the appearance of the testicles hanging lower.
While the positional change is largely cosmetic due to tissue laxity, the testicles themselves also undergo internal changes with advanced age. Mean testicular volume peaks around age 30 and stabilizes until about age 60, after which a significant decrease, known as testicular atrophy, can occur. This reduction in size is associated with a gradual decline in testosterone production and changes in testicular tissue.