William Aiken

Dear Dr. Aiken:

I just read your article on erections. Would it be possible to do an article on ejaculation? I am a healthy, trim, non-smoker, non-drinker of 45. My erections are fine but for the last two years there has been a noticeable reduction in the volume of seminal fluid. I would like to know what causes this and what can be done about it.

Dear Reader,

The volume of semen varies between 1.5 to 6 ml or roughly one-third to one teaspoon full. Seventy per cent of seminal fluid originates from a pair of glands situated between the bladder and rectum called the seminal vesicles. Another 20 per cent arises from the prostate gland and the remainder is composed of sperm cells and secretions from the testes and epididymes, respectively; the latter are tubular structures adjacent to the testes that store and transport sperm cells.

There are physiologic or normal reasons for variations in the volume of seminal plasma as well as pathologic or abnormal causes. Under normal circumstances, the volume of semen declines with advancing age related to declining levels of testosterone produced by the testes. The male hormone testosterone provides a stimulatory or tropic action on the accessory organs of reproduction such as the prostate and seminal vesicles.

Drugs that reduce the secretion of testosterone or prevent it from exerting its effects on the prostate and seminal vesicles will reduce semen volume. Examples of this include the drugs finasteride (Proscar¨) and dutasteride (Avodart¨) used to treat non-cancerous prostate enlargement. Other examples include anti-androgens such as Casodex and Androcur used to treat prostate cancer. Some drugs have an unintended anti-androgenic effect and may reduce semen volume. Examples include Cimetidine, used to treat peptic ulcer disease, and ketoconozole (Nizoral¨), an antifungal agent.

Gonorrhoea infection

There are mechanical factors that may cause not only a reduction in semen volume but also contribute to male factor infertility. These include ejaculatory duct obstruction (EDO) and retrograde ejaculation (RE). Acquired EDO is commonly due to scarring caused by infection from gonorrhoea, or prior prostatic inflammation.

Retrograde ejaculation occurs when semen flows backwards into the bladder instead of being propelled outside during ejaculation; this is due to incompetence of the bladder neck which in turn may be caused by prior surgical trauma, medications such as tamsulosin (Flomax¨) used to treat an enlarged prostate, and diseases which may affect the nerves that control closure of the bladder neck during ejaculation such as longstanding diabetes mellitus.

Overall, it is most likely that you are experiencing the normal age-related reduction in semen volume which requires no treatment, other than for you to make the necessary mental adjustment to its occurrence.