Introvert, gay personality. Be advised!

My son is 23 years old now. He has been very good in his studies, got admissions into IIT and completed his M.Tech from IIT-Bombay in June 2016. For the past 6 or 7 years, I have been observing that he has not been like any other boys of his age. He became very lazy, shy, not mixing with people and even relatives, silent, calm. We initially thought may be he is facing pressure of his academics and will be alright. Even after completing his hostel stay in IIT-Bombay, nothing has improved in his behaviour. He is living on his own world. He seems not serious in his career and life. Two years back he has opened up with us saying that he is a 'gay' personality and his sexual orientation is different from normal boys. We never discouraged him in any way. On his own he appears to be losing interest in life activities. He is not keeping friends. He tried for applying to some foreign Universities for doing PhD, but not pursuing at all. He needs to be advised