It is possible the fur loss could be caused by something else. The article below has a lot of info about hamsters and fur loss. 1.5 years isn't quite old age though. There are some completely bald hamsters who still live out their lives. I was told by a vet that they suspect Cushings when they have other symptoms like a swollen belly as well as hair loss and they tend to get sores as well, so I would keep optimistic and hope your hammy keeps well. Is he doing normal hamstery things and seeming happy in himself? What is the weather like in India at the moment, as yes they can moult in hot weather and have large bald patches - although your hamster has a bit more than just bald patches. It wouldn't do any harm to supplement the diet with a pinch of linseeds daily - give them separately in a separate dish or just loose on a house roof or platform eg. They seem to like them and eat them up. They work wonders for making coats thicker and glossier and good for skin as well. We have a rescue hammy who had bald patches and he now has a lovely thick coat after daily linseeds. It's a more natural way of providing some vitamins and essential oils. Also hemp seeds are chock full of vitamins and minerals so you could give a pinch of those daily as well (they won't make much difference to skin and fur like Linseeds but will help ensure he has enough vitamins and boost the immune system).
Hamster fur loss