Increasing Male Fertility and Longevity
The past 50 years have seen some amazing changes in the world. In 1953 a man who was 40 to 50 years old was already considered 'old' and well on his way to retirement. However, in 2003, being 40 isn't thought of by most (and especially those who have hit their fourth decade of life) as being old. It's now common to see 40-year-old men starting a 2nd or 3rd career, playing in professional sports or even being first-time fathers. Recent studies have indicated that the number of men aged 35 to 54 who are fathering children is up 20% in the past 20 years.
It's certainly heartening to realize that being past 40 doesn't mean a man can't enjoy the special pleasure of being a father. However, even in the 21st century, when the rules of aging are seemingly being rewritten on a daily basis, there are still some hard biological facts that all men must deal with. For those men who are trying to become a father, one of these facts is the decline in both the quality and the quantity of their sperm.
Infertility is not just a female 'problem'
Most couples will agree that one of the happiest times in their lives as husband and wife is when they first learn they're going to be parents. In fact, most couples take for granted their ability to have children and use birth control measures until they're ready to be parents. However, the truth is in the United States, at least 15% of all couples have great difficulty conceiving a child.1 While it's now known that in 30% to 40% of these cases this inability to conceive is due to male infertility, there is still a common misconception among both the lay population and the medical community that infertility is primarily a female 'problem.'
Female fertility testing/ treatment
Once a couple has decided to start a family, many become worried that 'something is wrong' after trying to conceive without success. This usually leads to a visit to their physician for testing. While the common definition of an infertile couple is one in which the woman has not become pregnant in one year of unprotected intercourse, many doctors will order testing in order to alleviate both the patients' and their own concerns.
With the rapid advance of medical technology, there are now multiple infertility tests and treatments for women. The problem is that these procedures can be extraordinarily expensive. In addition, emotionally and psychologically, these tests can put the entire burden of not being able to conceive on the woman when in fact, the man may be the cause of the couple's inability to conceive. Common tests and treatments such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) can cost $80,000 to $90,000 per procedure.2
For couples who are having trouble conceiving a child, it's quite reasonable to have the man checked first for reproductive problems. Most tests and treatments for male infertility are considerably less expensive than those for women. Simple tests for male infertility, such as semen analysis and ultrasound exam of the testicles, which can detect anatomical problems, cost in the hundreds, not thousands of dollars.
The 74-day life of a sperm
In order to more fully understand and appreciate male fertility issues, it's worth looking at the cycle of life from a man's point of view. The 74-day life cycle of sperm, the tiny, tadpole-shaped carriers of a man's DNA, is an amazing journey. Actually, one could argue that the life of a sperm begins not in the testicles, but in the brain, where hormones critical for reproduction are made. This biochemical cascade begins in the part of the brain known as the hypothalamus, which secretes gonadotropin-releasing hormone (GnRH). This hormone signals the pituitary gland to make follicle-stimulating hormone (FSH) and lutenizing hormone (LH). Normal levels of FSH act on the testicles to make sperm, while LH stimulates the production of testosterone. While it might seem on first glance that FSH is by far the most important of these hormones to maintain fertility, studies have shown that both FSH and LH (through its effects of stimulating testicular testosterone secretion), are needed for normal sperm output.4
In the testicles, the life of a sperm starts in one of several hundred microscopic coils known as seminiferous tubules. In lower parts of the seminiferous tubules are specialized areas called Sertoli cells, where sperm begin their development. As sperm mature, they leave the Sertoli cells and migrate up to the upper portion of the tubules, where they develop their characteristic head and tail. After this metamorphosis, the sperm are released into the epididymis. This remarkable 20-feet long C-shaped microscopic tube that envelops the testicle is contained in a space just one and a half inches long. It's in this tube, that has a diameter of only 1/300 of an inch, that sperm finish their maturation. During an orgasm, the sperm pass from the epididymis into one of two rigid, wire-like channels, the vas deferens. These channels join together just outside the prostate gland (which supplies the sperm with lubricating fluid to aid it on it's long journey) and form the ejaculatory duct. Finally, the ejaculatory duct empties into the urethra, which then empties out through the penis.
Are sperm in the western world
It's well known to physicians who deal with male infertility that the vast majority of male infertility is due to low sperm counts and/or poor sperm quality. What isn't as well known is that multiple studies have shown that in highly industrialized countries, sperm counts and sperm quality has been decreasing during the past 40 to 50 years. One of the most widely publicized studies showing a decline in sperm quality was published in the prestigious British Medical Journal in 1992 by Carlsen et al.5 The study was a meta-analysis of 61 studies done between 1938 and 1991 that examined sperm counts and sperm quality in men without a history of infertility. The results were startling: both sperm counts and sperm density showed significant declines between 1938 and 1991. This led the authors of the study to conclude that "as male fertility is to some extent correlated with sperm count, the results may reflect an overall reduction in male fertility."
As can be imagined, the results of this study were looked upon with skepticism by mainstream medicine, and in fact, several papers have come out that seriously questioned the validity of the Carlsen study.6 If the Carlsen report was the only study that showed a decline in sperm quality in industrialized western societies, then it's validity should be questioned.
Environmental toxins are unseen
Through the food we eat, the water we drink and the air we breathe, we are exposed to thousands of chemicals whose effects on human physiology are just now beginning to be understood. One way in which this chemical soup may be causing danger to the entire human race is by decreasing sperm counts.
An insidious way in which environmental pollutants may damage male fertility is through the production of free radicals, which are molecules produced inside cells in the body, including sperm cells, during normal cellular metabolism. While the body can produce some antioxidant scavengers to protect cells against free radicals, environmental pollution, and the resulting increase in free radical production it causes, this negative cascade can overwhelm the body's own defenses and allow free radical cellular damage to occur. In the case of sperm, elevated levels of free radicals have been linked to abnormal sperm density, motility, morphology and degradation of the sperm's outer membrane.11 Sperm are very dependent on the integrity and fluidity of this membrane for proper function, so damage by free radicals can easily lead to sperm death, and thus, seriously impair fertility. Studies have shown abnormally high levels of free radicals in the semen of 40% of infertile men.12,13
A group of chemicals that has received significant coverage in light of their possible negative effects on human health in general and male fertility in particular are endocrine disrupters. The term endocrine disrupters comes from the chemicals' ability to interfere with the normal functioning of the endocrine system, which is the system of ductless glands in the human body that secretes hormones into the blood. In terms of the reproductive system, the most well known hormones are estrogen and testosterone.
Clues that certain chemicals such as herbicides and pesticides can interfere with the normal functioning of the endocrine system began surfacing 30 years ago. In the 1970s, scientists working at the Thames River Water Authority in London observed that 40% of the male roach fish in the river were hermaphrodites (that is, they had both female and male sexual organs), and were thus sterile. In America, alligators exposed to pesticide runoff in Lake Apopka, Florida had multiple reproductive abnormalities, including smaller-than-normal penises and reduced fertility. Studies in rats have shown that female rats that are exposed to environmental estrogens produce male rat pups that have a significant reduction in their Sertoli cells, which are critical for sperm production.14 While no human studies have yet shown the same to be true in humans, it seems reasonable to think that this could very well hold true for people and could be another reason for declining sperm counts.
Besides affecting a man's reproductive system even before he is born, endocrine disrupters may adversely affect male fertility by decreasing testosterone levels. Adequate testosterone secretion by the Leydig cells (occur between the germ cells of the gonads) in the testis is essential for normal sperm production. Scientists in Britain have done studies on the estrogen-mimicking chemical HPTE, which is a metabolite of the commonly used pesticide methoxychlor. Through experiments done on rats, scientists have shown that HPTE directly interferes with testosterone production in the Leydig cells.15 Another way endocrine disrupters may harm sperm is by causing them to mature too quickly. A study released in 2002 presented direct proof that commonly used endocrine disrupting chemicals found in dozens of herbicides, pesticides and even paints can adversely affect a man's ability to impregnate a woman. In this landmark study, mouse sperm were exposed to a variety of common endocrine disrupters at levels that were roughly comparable to what a man living in the United States or Europe might have in his blood. After only 30 minutes, the majority of sperm exposed to the chemicals had matured too quickly, causing the sperm to lose the enzymes that are needed to enter an egg and cause conception.16
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