#1 he is 25 years or younger and his natural ability to produce testosterone is still functioning properly...so introducing an excess amount of testosterone could possibly be turning to estrogen in his body, thusly his sexual desires could be short circuiting due to hormonal confusion in his body.

#2 If he is taking more than the recommended dosage, the same effect as described above could also be happening.

I consulted my physician before taking androstenedione for personal reasons...basically the male hormone is a deterrent to disease and illnesses in the male body as well as a deterrent to prostrate cancer. I however have had asthma since birth and as an experiment with my doctor's consent, I tried androstenedione to see if it could lighten attacks. The physician suggested 25mg dosage instead of the standard 100mg the manufacturer suggests. This worked for me for the first 2 months, then we upped it to 50mg and now I am taking the max 100mg. I have been on this treatment for the past six months with no adverse effects. As a matter of fact my personal sex drive has increased as well as my asthma attacks being decreased to almost nil. So for the best suggestion if he is under the age of 25, STOP USING androstenedione for at least a year. If he is taking more than the max dosage then he should stop for 2 weeks and resume at a lot lower dosage say 25 or 50 mg per day, not more than once per day.