Quick Answer
Yes, it is completely normal for males to have two testicles or “balls.” The testicles are part of the male reproductive system and are responsible for producing sperm and testosterone. Most men are born with two testicles suspended in the scrotal sac below the penis. Having two testicles is part of typical male anatomy and does not indicate any medical issues on its own.
What are the testicles?
The testicles, also known as testes or balls, are oval-shaped reproductive glands in males that are part of the male reproductive system. The two testicles are contained within a sac of skin called the scrotum that hangs below the penis.
The testicles serve two main functions:
- Producing sperm – The testicles contain seminiferous tubules where sperm are produced. Sperm then mature and are stored in the epididymis located on the surface of each testicle before being transported through the vas deferens.
- Producing testosterone – Leydig cells in the testicles produce the male hormone testosterone. Testosterone is responsible for the development of male sexual characteristics during puberty and the maintenance of male features in adulthood.
In addition to sperm and testosterone production, the testicles also produce small amounts of estrogen and other hormones involved in sexual and reproductive function.
Why do men have two testicles?
There are a few theories as to why men evolved to have two testicles:
- Sperm production – Having two testicles allows for higher sperm production compared to having just one testicle. More sperm production improves fertility and reproductive success.
- Backup – The two testicles serve as a “backup” system in case one testicle becomes damaged or fails to function properly. This ensures continued testosterone and sperm production.
- Temperature regulation – The two testicles can more efficiently regulate temperature than one. This is important as sperm production requires a lower temperature than core body temperature.
- Physical protection – Having two smaller testicles in a divided scrotum provides more physical protection compared to having one large testicle.
So in summary, the evolutionary advantages of having two testicles likely include maximizing sperm production, providing redundancy, temperature control, and protection.
When does each testicle develop?
Testicle development occurs in several key stages:
- Around 6-7 weeks gestation, the early testes form from the genital ridge in the embryo.
- Between weeks 8-12, Sertoli cells differentiate within the testes and primitive sex cords form which will become the seminiferous tubules.
- By week 12-13, Leydig cells appear in the testes and begin producing testosterone which stimulates further male development.
- Between 15-25 weeks gestation, the testes descend from the abdomen into the scrotum.
- Sperm production begins around week 24 gestation.
So the two testicles develop independently as early as 6-7 weeks gestation, descending into the scrotum individually between 15-25 weeks.
Is it possible to have one testicle?
In rare cases, it is possible for males to develop only one testicle or testis. This condition is called monorchism. Estimates indicate monorchism affects less than 1% of males.
Causes of monorchism include:
- Failure of a testicle to properly descend into the scrotum during fetal development (undescended testis).
- Testicular agenesis – lack of development of one testicle.
- Orchiectomy – surgical removal of one testicle due to disease like cancer.
- Testicular torsion – twisting of the spermatic cord cutting off blood flow to testicle.
- Testicular trauma – injury to the testicle.
Monorchism can sometimes affect fertility and testosterone levels if the remaining testicle cannot adequately compensate. But many men with one testicle can still father children and have normal hormone levels.
Is it possible to have more than two testicles?
It is very rare, but some males may be born with more than two testicles. This condition is called polyorchidism or supernumerary testicles. Extra testicles occur due to abnormal division of the genital ridge during early fetal development.
The estimated prevalence of supernumerary testicles is 1 in every 20,000 males. In most cases, the extra testicle is nonfunctional and undescended. If three testicles are present, two are often located in the scrotum and one undescended. In extremely rare cases, all three testicles may be located in the scrotum.
Polyorchidism is often asymptomatic and discovered incidentally during surgery for cryptorchidism or a groin hernia. However, it can sometimes cause symptoms like pain or swelling from testicular torsion. Treatment may involve surgically removing undescended nonfunctional extra testicles.
Is it normal for one testicle to be larger?
It is common and normal for one testicle to be slightly larger than the other. Often the right testicle is larger, but the left may be larger as well. The size discrepancy is typically minor, on the order of 10-15% difference in volume.
Some key points about testicle size asymmetry:
- Most men have one testicle that is bigger due to natural variability in size.
- The difference is usually not noticeable and does not affect function.
- Size differences under 20% are not considered medically concerning.
- Significant size discrepancies or rapid testicle changes warrant medical evaluation.
- Benign conditions like varicoceles can sometimes cause larger size differences.
So mild testicle size asymmetry is normal, but men should talk to a doctor about substantial or progressive size differences between the testicles.
Table showing normal size ranges for testicles
| Age Group | Normal Testicle Size Range |
|---|---|
| 0-5 months | 1.6-2 cm length |
| 6 months – 3 years | 1.9-2.5 cm length |
| 4-6 years | 2.1-2.6 cm length |
| 7-10 years | 2.2-3.2 cm length |
| 11-14 years | 2.5-5.5 cm length |
| Adult | 4.5-6 cm length |
What disorders affect testicle development?
There are various congenital disorders and developmental abnormalities that can affect testicular development:
- Cryptorchidism – One or both testicles fail to descend into the scrotum by age 1.
- Hydrocele – Accumulation of fluid around a testicle causing swelling.
- Varicocele – Abnormal enlargement of veins around the testicle.
- Microlithiasis – Small calcifications within the testicle tissue.
- Hypospadias – Abnormal opening of the urethra on underside of the penis.
- Epispadias – Urethra opening on top side of the penis.
- Ambiguous genitalia – Incomplete male genital development.
These conditions may require surgical corrections like orchiopexy or orchiectomy in some cases. Proper testicular development is dependent on normal hormonal signaling and anatomy.
When should you see a doctor?
Men should see a urologist or doctor if they notice any of the following symptoms involving the testicles:
- One testicle notably larger than the other
- Change in size or lump/mass in testicle
- Pain, swelling, or redness of testicle(s)
- Firmness or hardness of testicle(s)
- Pain or swelling around the scrotum
- Feeling of heaviness or dragging in the scrotum
- Aching, tenderness, or discomfort in/around testicle(s)
- Fluid collection or swelling around the testicles
These types of symptoms can be signs of conditions like testicular cancer, testicular torsion, epididymitis, hydrocele, spermatocele, and others requiring evaluation. Sudden severe testicle pain should be regarded as a medical emergency.
Conclusion
It is completely normal for biological males to have two testicles as part of their reproductive anatomy. The testicles produce sperm and hormones essential for male sexual maturation and fertility. While it is possible to have one or more than two testicles in rare cases, most men have two testicles housed within the scrotal sac under the penis. Asymmetry in testicular size is common and normal as long as the difference is not significant. Men should see a doctor about any unusual changes, pain, or symptoms arising from the testicles, which could indicate an underlying medical condition requiring treatment.