micropenis

Penis size fixation is exploited on the internet with all sorts of bogus "treatments" and exercises. None of these are any good. Nor would I recomend penis extension surgery either.

I think your son should go for phychotherapy to help him with his self-image. He should also be open and frank with his next girlfriend about his size issue and make light of it. As Masters and Johnson said "It is not the size of the wand that makes the magic!" 

if you are thin and exercise a lot there is more testosterone and male hormones.  There is also better blood circulation to the penis.

If you are thin and exercise a lot there will be stronger harder erections .  This will lead to expansion of the penis.

another thing to watch out for is to avoid a lot of pressure on the penis in masturbation.  This causes energy to be diverted into repair rather than growth.

Also, make sure he avoids too much time on the computer.  The electromagnetic radiation from the monitor affects the brain and face.

I have been through the horrible torture of penis issues and do fully understand where you are coming from, but i will be firm and straight about the solution to the problem, the terrible truth is that you need to have something to satisfy the female partner, if your son doesn't have this it has to be put their, i went through 4 operations to save the penis i was born with, it was an inadaquate size , lacked structure and not usable, i had to agonise and decide if it was savable and could become something through surgery. if the penis is erect to less than 3 inches then really the only solution is to remove and reconstruct using whats known as a phalloplastic reconstruction, this requires an arm graft by taking the nerve endings from the inside of the arm and wrapping it around a synthetic phallus,and removing the original penis from the body,taking what ever nerve endings from the original ,biological penis as well, it is the very last resort and only done for severe small/micropenis, The UCHL near warren street london, has the best experts in penis issues and doctors there have years of experience. the micropenis is a mockery of the male gender and causes a deep unspoken pain, the Patent (one of them) link  is another option is https://www.google.com/patents/US7584757?dq=phalloplasty&hl=en&sa=X&ei=xOgEVJbXLIWP0AWM54G4Dw&sqi=2&pjf=1&ved=0CB0Q6AEwAA  

I am not a doctor , and so you should decide with the approapriate medical teams the best way forward, i'm simply telling you of my experience. 

Sadly i do feel the male gender to be under a massive disadvantage against the dominate female population. 

All the best to you.