In a positive-feedback system where hormone a alters the amount of protein x,

An increase in A produces and increase in X

This is a positive feed back mechanism. This mechanism enhance or amplify changes. This tends to alter the balance away from equilibrium because one hormone will increase the release of the other hormone. An example of this is the child birth. During labor, oxytocin is released to increase the uterine contraction the release of oxytoocin will be induced by the contractions of uterus. This will go on until the child was born. Just remember positive feedback enhance the original stimulus.

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