Does Heat Decrease Testosterone?
by Benjamin Bunting BA(Hons) PGCert
Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.
We thought that since testosterone is such a hot topic, we would share with you an article about the effect of heat on your levels.
This article will examine the effects of heat and how to keep your T levels up.
This article will teach you:
- What is the temperature of testes?
- Possible links between testosterone and heat
- Keep your ball cool with these 5 simple tips
Homeothermic animals are able to protect themselves against the cold through increasing their temperature and decreasing heat loss .
Our gonads work best at a temperature that is 2-4 degrees Celsius below the core temperature of our body .
Our testes have temperature-sensitive sensors to help us achieve this. The clever testes can move up or down depending on whether we're hot or cold. This is done via the cremasteric reaction.
It is also important that the temperature of our testes is kept at a reasonable level to ensure T levels do not drop.
Can too much heat reduce testosterone?
What is the scientific consensus?
Research has found that excessive heat can cause our testicles to shrink, which has an adverse effect on the quality of sperm.
Nakamura and colleagues  discovered that the temperature-sensitivity of DNA-synthesis is one of primary reasons for delicate thermal inhibition in human spermatogenesis. In other words, testes work best between 31-36 degrees Celsius (87-96 degrees Fahrenheit) and anything higher impacts T-levels and sperm levels.
According to Hjollund and colleagues , a high scrotal temp is common in patients who are infertile. Experimental studies have shown that certain types of exposure to high temperatures reduce the quality of semen.
It has been suggested that mild heating can also be used as a contraceptive method for men because of its effects on the quality of sperm .
Temperature and sperm quality
The temperature can have a significant impact on the size and fertility of testes.
What does this mean for our testosterone levels?
If animal studies have anything to do with it, then the answer is yes or possibly.
A study conducted by Lue and colleagues  examined the weights of testes following prolonged heat exposure (on rats - surprisingly, there weren't any human participants for this experiment!).
The researchers found that after 15 minutes of exposure to 43 degrees Celsius (109 degrees Fahrenheit), T levels dropped by 49% and testicular mass fell by 65%.
It is important to remember that humans and rats share almost identical testicular tissues, so we can easily transfer the findings to ourselves.
A second study  on boars showed that plasma testosterone levels decreased when the temperature was raised above 38degC. There also seemed to be some time delay between heating and T decreasing.
The evidence, however, is not conclusive. Hjollund  studied sedentary males who sat for extended periods of time and had excessively hot gonad temperatures.
They found that sperm counts decreased by 40% with every 1oC increase in daytime scrotal temp. The testosterone levels and quality of their sperm remained the same.
A study published in Norway in 2003 called 'Tromso Study'  found that the highest levels of men's free T were in December, while the highest levels of total T in October. The lowest levels recorded in June.
You can make a number of assumptions, but if you look at the testosterone peaks that occurred during colder months.
Testes and Heat
Research has shown that there is mixed evidence regarding the relationship between heat and testosterone. However, more than half of all studies claim heat reduces testosterone.
We've put together a list of quick tips to help you keep your T level high and cool. These are the tips:
1. Don't put your laptop on your knees
When placed on your knees, laptops generate heat and expose the balls of your feet to it. In order to place the laptop on your knees, you must also close your legs together. This will increase heat.
One study found that placing a laptop at the level of your knees can increase the temperature by 1degC within 11 minutes. It is best to place the computer on a table.
2. Avoid sitting down for prolonged periods.
Men are spending more time sitting, sometimes even with their legs crossed. This is not only bad for posture and your health, it can also affect your sperm.
The duration of work sitting positively correlates to daytime temperatures in the scrotum, and negatively correlates to semen quality.
You can expect your sperm count to decrease by 40 percent per degree Celsius increase. So, take frequent breaks and stretch.
3. Don't use saunas too often
Saunas are designed to provide a warm environment for the body. This can have a variety of health benefits. Even a single session in a sauna will expose sperms to very high temperatures. In one research study, it was found that after 20 minutes of sauna exposure for volunteers over a five-week period , sperm counts decreased.
4. Have cold showers
Bodybuilders have used these for many years, and with good reason. A cold shower not only revitalizes and refreshes you but it is also a Russian weightlifter's staple.
It's interesting to note that meat factory workers who are exposed daily (-40o C) showed a drop in serum testosterone  as well. So don't overdo it with the cooling!
5. Don't wear tight undergarments
While your white tighties might help you stay 'in-place', they could be damaging your sperm counts due to the heat restrictions. A study in Fertility & Sterility asked men to wear specially-designed underwear 14-16 hours per day for a period of 4 months.
Underwear held the testicles and scrotum very close to body, which heated them up significantly. By week four, the sperm counts of all the volunteers were drastically reduced.
After a "cooling-off" period of several months following the study, all participants recovered fully.
Our balls are low because our gonads work best at a temperature that is 2-4degC below the core temperature of our body. The body controls this by using the cremasteric reaction to determine whether the balls are positioned low towards the abdomen or high.
Keep your testes cool. Research shows that high temperatures, even for a short time, can impact the size and quality of sperm as well as our balls. Some evidence even suggests our testosterone can drop.
Avoid prolonged sitting, especially if your legs are crossed, or using your laptop while on your knees.
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- Sheynkin, Y et al. Protection from scrotal hyperthermia in laptop computer users. Fertility and Sterility. 2011 Feb;95(2):647-51
- Nakamura, M et al. Optimal Temperature for Synthesis of DNA, RNA, and Protein by Human Testis in Vitro. Archives of Andrology: Journal of Reproductive Systems. 1988; 20(1)
- Hjollund, NH et al. Impact of diurnal scrotal temperature on semen quality. Reprod Toxicol. 2002; 16(3): 215-21.
- Mieusset R, et al. The potential of mild testicular heating as a safe, effective and reversible contraceptive method for men. Int J Androl. 1994; 17(4): 186-91
- Lue, Y et al. Testicular Heat Exposure Enhances the Suppression of Spermatogenesis by Testosterone in Rats: The “Two-Hit” Approach to Male Contraceptive Development. Endoc. 1999; 141(4)
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- Solter M, Misjak M. Pituitary-gonadal response to extreme cold exposure in healthy men. Horm Metab Res 1989; 21(6): 343-344
- Ahmad, G et al. Mild induced testicular and epididymal hyperthermia alters sperm chromatin integrity in men.