_{A)          Those which are chemically identical to what is found in the body or are metabolized in one:  Most notable are the hormones, epinephrine (adrenalin), testosterone, esterfied estrogen, estradiol (an estrogen type natural hormone).}

_{B)         Those which are found in foods in bioactive amounts, such as the vitamins, glutamic acid, niacin, tryptophan.}

_{C)         And those which though structurally different mimic the action of hormones and are disposed of by the body in a similar way (without the serious side effects common of many foreign substances), such as amphetamine (antagonist of all adrenergic receptors), lysergic acid diethylamide (effects serotonin receptors), L-DOPA (precursor of dopamine),  estradiol}   

_{Listed are articles on those which fit this criterion and have consequences worthy of inclusion}