At first glance, the male reproductive system may seem a good bit simpler than the female system, in terms of the intricacy of its “machinery” and general function. But while men don’t release an egg every month or suffer from the grueling symptoms of PMS (or have the ability to carry a fetus, but who’s counting?), their reproductive systems are actually quite complex. Like the female system, men's sexual and reproductive systems are also governed by hormones released by the brain, various genes, and complex physiological mechanisms that underlie the whole setup. And let’s face it: the ability to develop and maintain an erection is truly a feat of physics that should be appreciated by all.

Let’s face it: the ability to develop and maintain an erection is truly a feat of physics that should be appreciated by all.

For most men the system is pretty robust, especially while they are young, and that is perhaps why many tend to overlook the delicate biological balance behind it. The complexity of the system becomes particularly apparent when problems arise. Some common male reproductive issues include premature ejaculation and erectile dysfunction (ED) – both are examples of disorders that can occur from time to time in the normal man, under normal circumstances. This article will outline how the male reproductive system functions overall, including its anatomy and physiology under normal conditions. It will also discuss some of the problems that many men may experience from time to time (like premature ejaculation and impotence) and some of the issues associated with the aging process and declining testosterone levels (is there such a thing as male “menopause”?).

The Sperm-Making Machinery

Similar to the female system, the male reproductive system is governed by the brain’s hypothalamus, a region that is responsible for basic physiological processes like sleep, hunger, and sex drive. And just as for females, the hypothalamus releases the hormone GnRH, which exerts its effects on the pituitary gland, sitting just adjacent to the hypothalamus. In response to GnRH, the pituitary releases the sex hormones luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which make their way to the testicles and affect sperm production.

The entire process of creating new sperm cells takes between 72 and 74 days to complete.

Cells in the testes called Leydig cells are responsible for making testosterone, and get their cue from LH to do this. Interestingly, cholesterol is the precursor of testosterone, meaning that it’s the building block from which testosterone is made, although there are several intermediate steps before testosterone itself is produced. (Unfortunately – or fortunately – this does not imply that men with high cholesterol will also have high levels of testosterone.) The hormone FSH signals the other main cell type of the testes, Sertoli cells, to begin producing sperm, in a process called spermatogenesis. The entire process of creating new sperm cells takes between 72 and 74 days to complete. Each day a typical man produces about 100 million new sperm cells, though this number may decline with age. When they are mature, the sperm cells begin their migration out of the testes by way of the epididymis and vas deferens, a process that takes about two weeks to complete. But before the sperm cells are ready to leave the body during ejaculation, they must pick up some additional fluids: these fluids come from the seminal vesicles, bulbourethral gland, and prostate, and together constitute semen.

The Mechanics of Erection and Ejaculation

For a man to be able to reproduce, sperm cells must not only be produced in great quantity, but they must have an effective way of getting out of – or being propelled from – the body. This is where erection and ejaculation come in. When a man is aroused, psychologically and/or physically, the brain sends signals to relax the smooth muscles in the penis which, in the flaccid state, are normally contracted. In other words, these muscles need to slacken in order for erection to be possible. In the flaccid state only enough blood enters the penis to bring oxygen and other nutrients to the tissues, but in the erect state, blood rushing in and essentially being “locked” in the penis, is what allows for and maintains an erection.

The nerves that travel from the spinal cord to the penis signal the release of nitric oxide, which is responsible for relaxing the smooth muscles of the penis. Blood can then enter the two “cavernous” spaces of the penis, called corpora cavernosa. Blood filling these cavities enlarges the penis and allows it to become rigid. Because the veins become compressed from the increasing pressure, blood is prevented from leaving the penis (this process is known as “veno-occlusion”), which is what maintains the erection.

Ejaculation and Orgasm
There are two phases to ejaculation: seminal emission and propulsatile ejaculation. Emission is the phase where the sperm cells move from the epididymus to the urethra (and at this point the bladder closes off so that sperm don’t move backwards into the bladder). The vas deferens contracts so that sperm is moved towards the prostate gland. The fluids picked up from the seminal vesicles, bulbourethral gland, and the prostate make up semen. When the semen moves further into the urethra and pressure in the prostate can be felt, this is known as the “point of no return” – when ejaculation in inevitable. Now, the second phase, propulsatile ejaculation, is set to occur. In this phase, contraction of the pelvic floor muscles, as well as the prostate, urethra, and seminal vesicles, propels the semen out of the urethra and out of the body.

But orgasms can occur, under certain circumstances, even when ejaculation or erection cannot, which suggests that the neuropsychology of orgasm is separate from the physical.

How does the psychological experience of orgasm relate to the physiological events described above? Orgasm happens, in large part, in the brain, and usually occurs at the same time as ejaculation. Unfortunately, despite the anatomical mechanisms of orgasm being well understood, not much is known about how orgasms actually occur in the brain. But orgasms can occur, under certain circumstances, even when ejaculation or erection cannot, which suggests that the neuropsychology of orgasm is separate from the physical.

In men who have had surgery to remove the prostate gland, orgasm can experience orgasm even without an ejaculation or even an erection. On the other hand, ejaculation during nocturnal emissions (a.k.a. “wet dreams”) often happens in the absence of any kind of physical stimulation, which implies that there is a purely cerebral component to orgasm. Additionally, people who have such neurological diseases as multiple sclerosis or Huntington’s disease can experience ejaculation without feeling that they have had an orgasm.

Most would agree that the psychological or emotional experience of orgasm is very real. It is thought that the brain pathways involved in orgasm and ejaculation are inhibited under normal conditions, so in order for these events to occur, these brain regions must somehow be “uninhibited” or released. What is clear is that the subjective experience of orgasm and ejaculation are two distinct events – and though they typically coincide in healthy men under most conditions, one can happen in the absence of the other.

Premature Ejaculation
Premature ejaculation (PE) is a common problem, particularly for young men who are sexually inexperienced. But it can also occur for men of all ages and experience levels. It can be either lifelong (chronic) or acquired (where the onset occurs later in life). It is defined by the American Psychological Association as “persistent or recurrent onset of orgasm and ejaculation with minimal sexual stimulation before, on, or shortly after penetration and before the person wishes it.”

The ISSM definition suggests that in lifelong PE, ejaculation usually occurs within one minute of penetration, a man is typically unable to delay ejaculation despite attempts to do so, and the phenomenon is accompanied by “distress, bother, frustration, and/or the avoidance of sexual intimacy.”[

Note that there is no specific amount of time within which ejaculation must occur to be considered “premature.” This has been criticized by some as a real shortcoming, as has the fact that other attempts to determine a time-frame for ejaculation have not arrived at anything concrete, possibly because the each definition is fairly subjective and not based on research. However, the International Society for Sexual Medicine (ISSM) arrived at its own definition after looking at many studies on PE. The ISSM definition suggests that in lifelong PE, ejaculation usually occurs within one minute of penetration, a man is typically unable to delay ejaculation despite attempts to do so, and the phenomenon is accompanied by “distress, bother, frustration, and/or the avoidance of sexual intimacy.” The ISSM feels that there is not yet enough evidence to come up with a good definition of the acquired form of PE.

In a sense, the time-frame isn’t so important. If a man and his partner feel that he is suffering from PE enough to negatively affect the couple’s sex life on a regular basis, then this is enough. Many men experience PE from time to time, and if it is a fairly rare occurrence, then this is considered normal and does not fall under the umbrella of “disorder.”

What causes the disorder? It usually has psychological or neurological origins, rather than being due purely to physical problems of the reproductive system itself. Anxiety about sex in general or performance anxiety may be causes, as can issues in which sex is associated with guilt or the need to rush to climax.

Treating Premature Ejaculation
Whatever the cause of PE, there are several methods of treatment, ranging from simple at-home techniques to more in-depth behavioral and medical solutions. One technique that the NIH discusses is the “stop and start” technique, in which stimulation of the penis is stopped when the man feels he’s about to orgasm to prevent ejaculation.

It’s usually recommended that stimulation is ceased for about 30 seconds, or until the man feels that an orgasm is no longer imminent. This process is repeated until an orgasm is desired. Another technique is the “squeeze” method, which is similar to the above, with the addition that when stimulation is stopped for 30 seconds, the penis is squeezed, either by the male or his partner, where the head of the penis meets the shaft. This suppresses the likelihood of orgasm, and can be repeated until an orgasm is wanted. Other “at-home” methods include using a condom, which can reduce sensitivity and therefore delay orgasm, or using an anesthetic cream on the penis, which may have a stronger effect. It’s important to talk to your doctor about proper application times, as leaving the cream on the penis for too long can have the opposite effect and make erection difficult or impossible to achieve.

Therapy may also work for men whose problems stem from specific psychological events or personal history. A therapist can help a man understand why the problem happens, as well as develop solutions for tackling it. Some of the goals of therapy may be to help the man become less anxious about sexual encounters, get back confidence in his sexual performance, and to open up the lines of communication between him and his partner.

Medications have also been used widely, particularly the group of antidepressants known as selective serotonin reuptake inhibitors (SSRIs), which include paroxetine (Paxil®), fluoxetine (Prozac®), and sertraline (Zoloft®). One of the side effects of SSRIs is diffiiculty achieiving orgasm. In the case of PE then, these drugs help reduce arousal and delay orgasm. Paroxetine may be the most effective of the SSRIs for the treatment of PE. It has been shown to increase the time before ejaculation by over 1400%, which is equivalent to a man being able to “last” almost nine times as long as he would without treatment. There may be additional approaches that can work for you or your partner, including alternative methods like yoga. In fact, one study showed that yoga was at least as effected as fluoxetine in lengthening the time it took participants to reach orgasm with their partners. As always, it’s best to check with your doctor about which treatment method will work best for you.

The Aging Process: Do Men Go Through Menopause?

Though female menopause is a no-brainer, the idea of male menopause is a little trickier. In women, the hormonal changes that come when ovulation ceases occur over a fairly short period of time – a few years, or less, in most cases. And these changes clearly have a dramatic effect on a woman’s overall mood and sexual health. Men, on the other hand, don’t have this kind of abrupt change in hormone levels. Testosterone levels decrease subtly over a period of many years, beginning at around age 30. And while females are incapable of conceiving after menopause is complete, male fertility is affected in a much less dramatic way (we’ve all heard of men conceiving children well into their 80s or even after).

Testosterone levels decrease consistently, by about 1% per year after the age of about 30, and by the time men are in their 70s, their testosterone levels are only about 50% of what they had been at their highest.

Let’s Call It “Andropause”
Some researchers have dubbed the subtle changes in male hormone levels over time “andropause,” though there is more debate over its nature than there is with menopause, which is more clear-cut. Testosterone is the main male sex hormone and is responsible for many aspects of their sexual health, including both the biology and the behaviors associated with sex and reproduction. But testosterone levels decrease consistently, by about 1% per year after the age of about 30, and by the time men are in their 70s, their testosterone levels are only about 50% of what they had been at their highest (which is usually when a man is in his 20s). The loss of testosterone occurs largely because the testosterone-producing tissue of the testicles (made up of Leydig cells) diminishes with age. But there is also some decline of GnRH secretion from the hypothalamus itself, as well as a decrease in sensitivity of the Leydig cells to the hormones LH and FSH. The resulting reduction of testosterone levels may lead to a decrease in libido as a man ages, as well as some non-sexual effects like decreases in bone mineral density (osteopenia), decreases in muscle mass, and cognitive decline. In this sense, there is some similarity between “andropause” and menopause. There is little evidence, however, to suggest that testosterone replacement therapy has a the same degree of effectiveness as hormone replacement therapy in women.

Fertility: Reproducing into the Golden Years
Though men are theoretically fertile for the entirety of their lives, sperm count does tend to decrease a bit over time, which correlates to decline in fertility over the years. This is just another part of the normal aging process. One study found that in men between the ages of 22 and 80, semen volume, sperm count, and sperm concentration all declined somewhat over time. The number of motile (active) sperm decreased significantly as the men aged, whereas the number of abnormal sperm increased. The authors of the study say that the numbers correspond to a 50-year-old man producing about 28% fewer motile sperm than a 30-year-old man. Though older men are still making many millions of normal, active sperm per day, believe it or not, the reduction actually translates to a fairly big drop in fertility. Another study found that men over the age of 35 had half the chance of getting his partner pregnant with in a 12-month period than did men under the age of 25. (These results were true after the women’s age had been controlled for.) So, though men are certainly capable of fathering children well into their golden years, it may be just take a little longer for them to do so.

Erectile Dysfunction

Most often erectile dysfunction (ED) is just an unfortunate side-effect of the natural aging process. In fact, one study found that over 50% of men between the ages of 40 and 70 suffered from some form of ED (partial or complete). Estimates suggest that somewhere between 20 and 30 million men suffer from ED in the United States, meaning that it is in no way a rare occurrence.

Primary ED is very rare, and generally due to psychological, rather than biological, causes (for instance, extreme anxiety or intimacy issues may cause a man to be unable to get or sustain an erection). Many cases of ED are actually secondary to other disorders like diabetes or high blood pressure. It’s estimated that about 70% of all instances of ED are secondary to other diseases, with diabetes being one of the most common causal factors.

What Causes ED?
In the normal aging process, degeneration of the body’s blood vessels naturally occurs, in a condition called atherosclerosis, and this includes the blood vessels of the penis. If the arteries lose their flexibility with age or disease, they are unable to relax sufficiently to allow the blood flow necessary for an erection, and ED may occur. Additionally, even if an erection can happen, leaky veins may not allow for the erection to be sustained because the blood cannot be “locked” in the penis. Because blood vessel degeneration is so common in diabetes, somewhere between 35 and 50% of diabetic men may experience ED.

Drugs may also cause ED, including antidepressants like the SSRIs mentioned earlier, as well as monoamine oxidase inhibitors (MAOIs) and tricyclics. Another class of drugs that can lead to ED is the antihypertensive (blood pressure) medications like beta-blockers and clonidine.

Other diseases and conditions like multiple sclerosis, Parkinson’s disease, stroke, seizure, and various neurological or endocrine (hormone) disorders may also lead to ED. Alcohol, nicotine use, and being overweight or obese, are also associated with ED. Prostate surgery is a frequent cause of ED.

Though testosterone levels naturally decline with age, it is unlikely that this decline alone would cause ED; in the case of lower-than-normal testosterone levels, decreased libido may actually be the underlying factor for ED. Some men may have a little success with testosterone replacement therapy, though this number appears to be fairly small.

Another 10-20% of ED cases may stem from psychological issues, like chronic stress, depression, performance anxiety, relationship strain, and problems with sexual arousal.

Treatments for ED
The Drugs
The most common course of treatment for ED is the class of drugs known as phosphodiesterase-5 inhibitors (PDE-5). The best-known and first to enter the market was sildenafil citrate (Viagra®), but more recent additions include vardenafil HCl (Levitra®) and tadalafil (Cialis®). All three work in similar fashions, and that is to increase the release of nitric oxide, which, as mentioned earlier in the article, allow the smooth muscles of the penis to relax and encourage blood flow. About 80% of men experiencing ED have had success using this kind of medication. The drugs are usually taken about an hour before sexual activity is anticipated.

Some side-effects have been noted with the drugs, which have generally been found to decrease over time. These may include stuffy nose, headache, flushing, stomach upset, light sensitivity, and muscle aches. One odd side-effect of sildenafil and vardenafil is a “blue-green” tint to the vision. As many have heard in the commercials for the medications, if you have an erection lasting more than four hours, it’s important to call your doctor.

These medications have been shown to be safe and effective, for the most part, but as always it’s crucial to talk to your doctor about other medications you’re currently taking, just in case there is an interaction between it and the ED drug. Nitrates should not be taken with any of the ED drugs, as doing so can cause an abrupt and dangerous drop in blood pressure (hypotension). Men who take blood pressure medications, alpha-blockers for enlarged prostate, or blood thinners should also not take PDE-5s.

Other Treatments
Another effective therapy for men who can’t use, or do not respond to, the PDE-5 drugs is alprostadil, which is self-administered either via an injection directly into the penis or through a small catheter into the urethra. The drug, administered in the injection method, works in about 80-90% of men who use it.

Other treatments include mechanical devices (including vacuum devises and penis rings), pumps, and even prosthetic surgery in more serious cases of ED. Therapy may work for some men whose problems stem from psychological issues or specific events in the past. Making lifestyle changes may also have a surprisingly strong effect – such changes would include stopping smoking to improve cardiovascular health, weight loss, exercise, and reducing alcohol consumption. Again, it is important to discuss with one’s doctor what forms of treatment will work best given the type of ED one is suffering from (and again how any current medications may interact with the common prescription ED drugs).