explain feed back mechanismwith an example

A feedback mechanism is a process  where the level of one substance influences the level of another substance or activity of another organ

Eg - Regulation of blood glucose level by insulin.

An increase in blood sugar level triggers the release of the hormone insulin by the pancreas. Insulin increases the ability of body cells to take in glucose from the blood and converts blood glucose to glycogen. Thus it lowers blood sugar level and restores the original blood glucose level of the body.