In medicine, large volume of semen (hyperspermia) is a condition in which a male has an abnormally large ejaculate (or semen) volume is called hyperspermia. Males with hyperspermia usually have higher sex drives than males that do not. It is the opposite of hypospermia (low semen volume), and is generally defined in humans when the ejaculate is over 5.5 ml.

In most cases, hyperspermia does not interfere with fertility. If the semen contains an adequate concentration of healthy sperm, higher volumes actually enhance fertility, respectively.

Mature sperm cells in the testes that are ready for ejaculation pass through the epididymis (tube that holds the testicles in place; Pic. 1) where prostate fluid, which is rich in proteins and other factors such as citric acid and zinc, is added. Prior to release, semen is further augmented by fluid from the seminal vesicles, which are responsible for establishing the alkaline pH of semen. 

The average volume of seminal fluid ejaculated is 3.5 ml, but can range anywhere from 100 μl to 11 ml. Just as the total volume varies, the concentrations of biologically active factors (including hormones, mucin, cadaverine, putrescine, spermine, enzymes, cytokines/chemokines, fructose, and vitamin D), and other soluble factors present in seminal fluid, can also vary significantly within one individual over time. 

Semen content can also be affected by other factors, such as changes in fertility, age, frequency of ejaculation, infection by sexually transmitted disease (STD) pathogens, substance abuse, prescription medications, and other factors that reflect an individual's lifestyle. 

The physical examination of the ejaculate includes measuring of the semen volume, assessment of viscosity, general visual appearance and odour. A small volume is from the bulbourethral glands (pea shaped glands that add fluids to semen during the process of ejaculation), epididymides and prostate (first part) and the major volume contribution is from the seminal vesicles (second part). Precise measurement of volume is essential to calculate the total number of spermatozoa and non-sperm cells in the ejaculate. 

Sperm concentration refers to sperm numbers/ml and total sperm number refers to the total number of sperm in the entire ejaculate (volume x sperm count/ml).

The impact of hyperspermia on fertility depends mainly on the concentration of sperm in the ejaculate. In most cases, hyperspermia does not severely compromise fertility. If the amount of sperm is proportional to the volume of seminal fluid, hyperspermia can actually increase fertility of the male. If the semen is thinner, however, the sperm becomes more diluted and the chances of fertilization of the egg are lower. Also, if hyperspermia follows a period of longer sexual abstinence, the semen may contain a higher proportion of dead and damaged sperm, which cannot fertilize the egg. Some men experiencing hyperspermia can therefore suffer from infertility.

Sources

The interpretation of a semen analysis ―by Bornman licensed under CC BY-NC 3.0
Hyperspermia ―sourced from Wikipedia licensed under CC BY-SA 3.0
Influence of ejaculation frequency on seminal parameters ―by Mayorga-Torres et al. licensed under CC BY 4.0
Hyperspermia ―sourced from Fertilitypedia licensed under (CC BY-SA 4.0)
Epididymis-KDS ―by KDS444 licensed under CC BY-SA 3.0
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