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Does Heat Decrease Testosterone?

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Testosterone is a ‘hot topic’ so we thought we’d share an article on the effects of heat on testosterone levels with you.

In this article we’ll take a look at the science behind keeping your testosterone levels high by keeping your balls cool, and the consequences of heat on T levels.

In this article you learn:

  • How we regulate temperature in the testes
  • The possible links between heat and testosterone levels
  • Top 5 tips for keeping your balls cool

Regulating heat

‘Homeothermic animals protect themselves from the cold by increasing the temperature and decreasing heat losses’ [1].

There’s a reason why our balls hang low – our gonads function optimally just below our normal body temperature, around 2-4°C lower than our core body temperature in fact [2].

In order to achieve this our testes are temperature sensitive. They have the clever ability to hang low or move upward dependent on how hot or cold we are – this is via a process called the cremasteric reflex. 

And given that our body produces testosterone is the testes, it is important to keep them at a comfortable temperature to make sure T levels aren’t affected.

Does too much heat decrease testosterone levels?

Let’s have a look…


What does the science say?

Some research has shown that our testicles can shrink when presented with excessive temperatures, and that has a drastic effect on sperm quality.

For example, Nakamura et al [3] found that temperature sensitivity of DNA synthesis may be one of the primary causes of delicate thermal inhibition of human spermatogenesis- in other words, our testes function best at 31-36 °C (87-96 °F) and anything above this impacts sperm production and likely T levels too. 

In fact, according to Hjollund et al [4] a high scrotal temperature is a common finding in infertile patients and experimental studies indicate that specific types of high temperature exposure reduce semen quality. 

In fact, mild heating has also been proposed as a method of contraception for men due to its effect on sperm quality [5].


Temperature-and-Sperm-Quality

Key Point: Excessive temperatures can affect the size of your testes, as well as fertility.


Does that mean then that our testosterone levels will fall too?

Well if animal studies are anything to go by, the answer appears to be yes, or at least possibly.

Likewise, a study by Lue et al [6] investigated the weight of the testes after prolonged exposure to heat (on rats, surprisingly there were no human volunteers for this one!). They found that when exposed to 43 °C (109 °F) temperature for 15 minutes, T levels plummeted (49%), and a massive 65% reduction in testicular weight occurred.

A point to note is that rats and humans share pretty much identical testicular tissue so the results are pretty transferable to us.

Another study, this time on boars [7], showed that when testes are presented with a heat up to 38°C there is no change in T levels, but when temperatures rise above that level, plasma testosterone decreased- there also appeared to be a time lag from heating to the point when T decreased. 

However the evidence isn’t completely conclusive. Hjollund and colleagues [4] investigated sedentary men sitting for long periods and with excessively high gonad temperature, and found that whilst sperm concentration decreased 40% per 1ºC increment of daytime scrotal temperature. Their testosterone and sperm quality remained unchanged. 

There was an interesting study called the ‘Tromsø study’ [8] based in Norway published in 2003- the study found that men’s total T levels were highest during the months of October and November, and free T was highest in December- with lowest recorded levels being in June.

Now there’s a lot you can speculate here- but looking at these peaks in testosterone, they all occurred in the coldest months.


Testes-and-Heat

Key Point: According to research, the evidence between heat and testosterone levels are mixed – with more studies than not claiming that heat lowers testosterone levels.


How to protect yourself

In order to keep your balls cool, and keep those T levels high we’ve compiled a short list of tips. Here they are:

1.Don’t put your laptop on your knees

Laptops are active heat-generating devices that expose your balls to the high temperature of the machine when placed on the knees for extended periods of time. Additionally, in order to hold the device on your knees you have to close your thighs together which also contributes to elevated heat.

In one study [2] it was found that a laptop on the knees increased temperature of the testes by 1°C in 11 minutes so best to avoid it and place it on a desk.

2.Don’t sit down for long periods of time

More and more men have a sedentary work position which means extended periods of time sitting down – sometimes with the legs crossed. Not only is this bad for your overall health and posture, but this sort of position can play havoc with your sperm quality too.

According to Jung et al [9],‘duration of sitting during work positively correlates with daytime scrotal temperatures and daytime scrotal temperature negatively correlates with semen quality’. 

If you sit down all day you could expect sperm concentration to drop by 40% per 1ºC increment increase, so where possible have little breaks, stretch your legs and cool down a bit.

3.Don’t use saunas too often

The purpose of a sauna of course is to present the body with a hot environment – and there are a number of benefits that you might get from this. However, even a single sauna can exposure sperm to high temperatures. One research paper found that when volunteers were exposed to 20 minutes in a sauna, sperm numbers fell for a 5 week period [10].

4.Have cold showers

These have been popular with bodybuilders for years – and rightly so. Not only does a cold shower revitalize and refresh you, it has been a staple routine in Russian weightlifters for years.

Interestingly, meat factory workers exposed daily to extreme cold (-40º C), showed a decrease in their serum testosterone levels too [11] – so don’t go too far with your cooling methods!

5.Don’t wear tight undergarments

Whilst your tightie whiteys might keep you ‘in place’, the restrictions on heat control might be putting your sperm count at risk. In a study published in Fertility and Sterility [12] men were asked to wear specially designed underwear for 14 to 16 hours a day over a 4 month period.

The underwear kept the scrotum and testicles very close to the body and of course this heated the testicles significantly. The results of the study reported massive decreases in sperm count by week 4, and by the end of the study practically all volunteers had a zero sperm count. 

Luckily, after a ‘cooling off’ period of a few months after the study, recovery in all volunteers was full.


Summary – Does heat decrease testosterone?

There’s a reason why our balls hang low- our gonads function optimally just below our normal body temperature – around 2-4°C lower than our core body temperature in fact. To achieve this, the body uses the cremasteric reflex to control whether our balls hang low or higher towards the abdomen dependent on their temperature.

It is important to keep our testes at a comfortable temperature as research suggests that prolonged or sometimes even short-term high temperatures can affect the size of our balls, as well as sperm quality – there’s even some evidence to suggest that our testosterone levels can fall too.

In order to keep cool, you can have regular cold showers, and avoid anything that could heat your testicles such as prolonged sitting – particularly if you cross your legs – and using a laptop on your knees.


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References

  1. Pääkkönen, T et al. Cold exposure and hormonal secretion: a review. Int J Circumpolar Health 2002; 61: 265-276)
  2. Sheynkin, Y et al. Protection from scrotal hyperthermia in laptop computer users. Fertility and Sterility. 2011 Feb;95(2):647-51
  3. 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)
  4. Hjollund, NH et al. Impact of diurnal scrotal temperature on semen quality. Reprod Toxicol. 2002;  16(3): 215-21.
  5. 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
  6. 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)
  7. Stone, BA et al. Effects of acute and chronic testicular hyperthermia on levels of testosterone and corticosteroids in plasma of boars. Animal Reproduction Science. 1984; 7(5): 391-403
  8. Svartberg J et al. Seasonal variation of testosterone and waist to hip ratio in men: the Tromsø study. J Clin Endocrinol Metab. 2003; 88(7): 3099-104.
  9. Jung A, et al. Influence of genital heat stress on semen quality in humans. Andrologia. 2007; 39(6): 203-15.
  10. Brown-Woodman, PD et al. The effect of a single sauna exposure on spermatozoa. Arch Androl. 1984; 12(1): 9-15.
  11. Solter M, Misjak M. Pituitary-gonadal response to extreme cold exposure in healthy men. Horm Metab Res 1989; 21(6): 343-344
  12. Ahmad, G et al. Mild induced testicular and epididymal hyperthermia alters sperm chromatin integrity in men.