Of course everyone knows that humour reduces stress etc, but I think rarely do people know the process behind it. Since I was interested, I did a search pertaining to laughter/comedy reducing cortisol levels (and thereby possibly increasing T levels marginally) and came up with this. Interesting article if you have the time to read:
http://serendip.brynmawr.edu/bb/neuro/neuro02/web2/mdrejka.html
In short, if you have high cortisol levels, stop walking around with a scowl on your face and try and lighten up a bit