Though transplanted hair stay forever and grow naturally but in some cases these transplanted hair falls after 2-5 years later. There are various reasons for this transplanted hair loss.
1- When you have hair transplant, your surgeon added more grafts in your existing hair. As time pass your own hair fall and as a result thinning of hair and you are feeling hair loss of transplanted hair
2- If you have hair transplant on your bald area and previously this area does not have any hair, usually hair loss start 2 to 5 years after hair restoration procedure and this phenomenon is called synchronization. You do not need to worry as after 6 months losing transplanted hair, you will see regrowth of those hairs. However to speed up their growth you may start Propecia and Minoxidil lotion or foam.
3- Despite all medical hair restoration efforts, you are not getting satisfactory response then another session of hair transplantation is recommended. This session will be to add more hair density in your transplanted hair.