Thanks for query,
If you have deficiency of some vitamines,Iron,and zinc etc elements ,you may have thin and under nourished hair.
Take high protein diet,green veges,fruits,
Take vit A,D,E and Iron.
Take more milk,water,
use branded hair oil containing vit E.,use good conditioner.
If you have problem on scalp
like dandryff,fungus,treat them.
ok and bye.