Is thinning hair also an early sign of hair loss?

My hair feels weaker than before, and when I tie it up, the knot feels thinner.

I'm not losing a noticeably large amount of hair, but I'm wondering if a change in hair thickness could be an early sign of hair loss.

In this case, I would like to know if checking only the number of hairs falling out is sufficient, or if I also need to examine the scalp or check for changes in hair thickness.