Is there any known substance that can decrease fertility of a male?
Less specifically what about one time chemical castrations (ignoring a perfect sterilization)?
I heard about them before once but wasn't sure really.
Is there any known substance that can decrease fertility of a male?
Less specifically what about one time chemical castrations (ignoring a perfect sterilization)?
I heard about them before once but wasn't sure really.
Numerous chemicals are linked with decreasing male fertility. In fact, studies suggest that unhealthy lifestyles and environmental factors (e.g. plasticisers in the water system) may be causing this decrease in fertility. See: http://www.telegraph.co.uk/men/active/mens-health/10695991/Why-are-mens-sperm-rates-falling.html etc Obviously conclusive studies are limited at this stage.
But if you want to be more specific, I recall that chloroform is known to cause miscarriages and sterility in mice. Googling that to find a citation led me to this article: http://www.ncbi.nlm.nih.gov/pubmed/10969727 Which found evidence of an otherwise non-toxic antifertility agent for male rats.
To be honest, I would be surprised to find studies which have tested a anti-fertility drug on men. Such a thing should not make it past an ethics board (given the ability to prevent impregnation by far less drastic measures, e.g. condoms).
If however you were talking about the sort of chemical castration they did to someone like Alan Turing, they were not designed to sterilise him (heck, his 'crime' was homosexuality and children were not a likely outcome of that), but to alter his hormones and personality. Anyway, modern drugs might be something like Cyproterone acetate or Depot medroxyprogesterone acetate - though that is also used as a birth control drug for women.
Be it surgical or pharmacological, sterilization is a way to prevent conception, whereas castration is a suppression of the testes (emasculation). Infertility can be achieved with an intervention on the testes or on other reproductive organs (prostate, seminal vesicle, vas deferens).
Testes not only produce sperm but also androgen hormones (testosterone), which have a plethora of effects on the body, the behaviour, etc. Sperm is made from germ cells and testosterone is produced in Leydig cells.
Antiandrogenic interventions (hormonal or metabolic) will block testosterone (possibly irreversibly, see finasteride). This will affect sperm production, but will also result in androgen deficiency.
Cytotoxic chemicals used in chemotherapy (e.g. cisplatin) affect sperm production, which involves many germ cell divisions. But this is also likely to damage the Leydig cells.
Papaya extract action on sperm motility is reversible.
There are several ongoing studies for male contraceptives (have a look on Wikipedia). One of the big problems though is to reverse the effects.
VasalGel is thought to hit the market by 2018. It is a gel that physically blocks the sperm once injected in the vas deferens but can be washed out to revert its effects.