October 2012 - Page 2 of 2 - Hormones Matter

Male Contraception

Published on October 7, 2012

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How many women do you know that use birth control pills as their primary form of contraception? A recent analysis by the Guttmacher Institute reports that 18% of all women in the U.S use some form of oral contraception. Quite a few!

What would happen if there was an equivalent form of contraception for men? Would it be as popular? Would it be as reliable? Researchers are trying to develop the technology to answer these questions.

Anything but a Vasectomy!

Aside from condoms, other forms of male contraception have been around for a while. Some methods of contraception seek to physically block the vas deferens, or the path for sperm to exit the urethra. For example, the Pro-Vas clip is used as a mechanical block for sperm by clamping the vas deferens, essentially doing the same thing as a vasectomy – without physically severing the sperm duct.

Another method uses a chemical polymer to block the passage of sperm to the urethra. This polymer, known as styrene maleic anhydride, has entered phase III clinical trials in India. Lisbeth Prifogle goes into more detail about the exact mechanism used for this type of contraception in her article, Male Birth Control – Myth or Available Science.

Whether mechanical or chemical, these methods introduce drastic and potentially harmful changes to the male reproductive anatomy. Although the manufacturers claim that these treatments are completely reversible, as a male, I would be hesitant to adopt such measures as I suspect other men would be. Oral contraception is a more attractive method.

Oral Male Contraceptives

Oral contraception used by men is nothing new. Since the early 20th century, a natural product from the cotton plant known as gossypol, has been used as a male contraceptive, particularly in Asian countries. Due to concerns of toxicity and side effects, however, gossypol has never been approved as a contraceptive by the FDA.

Since the mid-1980s, research led by the World Health Organization to develop a hormone-based birth control pill for men has resulted in a better understanding of the male hormonal system, and what biological targets are most attractive for male contraceptives. Much like the female birth control pill, which works by controlling the levels of the hormones estrogen and progestin, these birth control pills also work by introducing exogenous hormones into the body. These types of pills have been called Male Hormonal Contraceptives (MHCs).

The primary form of MHC is a form of testosterone named testosterone undecanoate. Using testosterone as a contraceptive was counterintuitive for me because when I think of high testosterone I think of an increased libido. But as it turns out, an extra shot of the hormone results in a decrease of the signaling hormones responsible for spermatogenesis (sperm production). Although testosterone treatment does seem to induce azoospermia (the absence of motile/viable sperm), there is no MHC that is currently in clinical trials – it seems that this pill is quite a ways off.

A New Type of Pill

There have been a few other pills that have been proposed as male contraceptives that don’t use hormones – one of the most interesting new studies to come out was an anti-cancer drug that was accidentally discovered to have spermatogenic effects. Many of the compounds developed in these studies, including anti-cancer drug compounds, target and inactivate specific proteins that are necessary for biological function.

In this study, which was published in the journal Cell last August, the compound tested, which is called JQ1, binds and inactivates BRDT, a protein that is specific to the testes and is involved in an essential DNA-based process called chromatin remodeling. The result, as observed in mice, is that as long as the organism was administered the drug, although they mated, there was a complete and reversible contraception.

So it seems that many new technologies are being developed for men to share the responsibility of contraception. However the question still stands: Can they be trusted?

Neurogenesis – A Result of Hormones?

by Elena Perez

Published on October 3, 2012

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Studies have shown that exercise promotes learning and neurogenesis, or the creation of new brain cells, but exactly what’s going on is still being worked out. One group of scientists, however, think they’re on the right track.

Researchers from the University of Tsukuba, the University of Tokyo, and The Rockefeller University considered a number of studies that have shown that hormones have more to do with our brains than previously imagined.

Hormones Produced in the Hippocampus

In the past, androgen hormones were thought to be produced solely in the testes and carried to the brain via circulation, but several studies have revealed that androgens can actually be made in the hippocampus, the part of the brain that is associated with forming and storing memories.

In 2010, Endocrinology published a study that found higher levels of sex hormones in the hippocampus than in the circulatory system of rats. Furthermore, even when the rats were castrated at birth, there was not a significant reduction of sex hormones in specific regions of the brain, leading scientists to believe that specific sex hormones are not only important for gender development, but for brain development as well.

Hormones Linked to Brain Plasticity

Recently, more scientists have been pursuing research that links hormones to brain development. In 2006, researchers from Yale discovered that androgens affect hippocampal synaptic plasticity.

There are billions of neurons in our bodies, and we rely on these cells to transmit information to other cells via synapses so that we can function. The more efficiently our neurons respond to messages, the more effectively our bodies function. Luckily (or unluckily) for us, scientists have discovered that this responsiveness can change – depending on how often we put our neurons to work.

The more we use certain synaptic pathways, or the structures that transmit information between neurons and other cells, the more they are strengthened – literally becoming engraved in our minds. Not engaging these synaptic pathways, however, results in slower responding neurons and cells.

The ability of synaptic pathways to become more or less responsive is referred to as synaptic plasticity. In the case of the neuron, the adage “practice makes perfect” or “use it or lose it” rings true. It’s no wonder that synaptic plasticity is associated with learning and memory.

But our ability to learn and remember is not solely based on how often we use certain synaptic pathways; the plasticity of the brain seems to be hinged on sex hormones, too.

The scientists from Yale found that when the testes were removed from rats, there was a significant decrease in the number of synaptic pathways. Yet these pathways were replenished when the castrated rats were treated with androgens. They found similar outcomes with ovariectomized female rats, but female rats rely more on endogenous estrogens, so weaker androgens were sufficient for rebuilding synaptic pathways.

Though scientists are still trying to understand the exact mechanisms involved with brain development, they have begun to recognize how important sex hormones are to brain development and our ability to learn.

Researchers Connect Exercise to Hormone Production

Building upon previous research, the scientists from Japan and New York proposed that exercise actually increases the production of androgenic hormones in the brain, and that this increase in sex hormones promotes neurogenesis. The study was published in the Proceedings of National Academy of Sciences, and the results sparked excitement.

In order to ensure that the androgen hormones were produced in the brain and not the testes, the researchers castrated some of the rats. Although the remaining test group of rats were not castrated, they still underwent a surgical procedure so that conditions and stress levels did not vary between the two groups.

There has already been research showing that the female sex hormone, estradiol, is involved in neurogenesis, so the scientists decided to focus on the male sex hormones. To ensure that testosterone was not being converted to estradiol, the researchers blocked the estrogen receptors with tamoxifen, a non-reactive binding agent, so estradiol could not be taken up in the brain.

The researchers found that after exercise, the androgen dihydrotestosterone increased significantly in the brains of the rats – even in the castrated rats. They also found an increase in the number of neurons in the hippocampus – and the results did not change in the rats that were treated with tamoxifen.

Some rats, however, had specific receptors blocked so that they could not use the dihydrotestosterone in the brain. The scientists were surprised to find that these rats did not experience neurogenesis, leading researchers to believe that dihydrotestosterone is not only produced as a result of exercise, but is also necessary for the production of new brain cells.

Though there is still much more research to be done (the researchers only experimented with male rats, for starters), the study demonstrates the complexity of our bodies and the hormones within us. As for me, I feel more compelled to exercise before I learn something new – hormones help me.