There is feedback mechanism by which …

Feedback mechanism is the mechanism of the body to maintain the levels of hormones in the body in the desired limits. An increase or decrease in the levels of the hormones triggers the feedback mechanism. 

The body has two types of feedback mechanisms, positive and negative feedback mechanism.

Example:

Negative feedback mechanism: 

Whenever there is a change in the normal state, the messages are sent to ‘increase’ secretions if there is a fall below normal or to ‘decrease’ secretions if there is a rise above normal to restore the normal body state. Such a mechanism is called a negative feedback mechanism.

The increase in the blood sugar level stimulates the secretion of insulin so that the sugar level is maintained. If the blood sugar level falls below normal, then it stimulates the secretion of glucagon. Glucagon stimulates the breakdown of glycogen to glucose, and thus, the normal sugar level is maintained.