A substance that tastes bitter to some people but is tasteless to others. The ability to taste it is thought to be an autosomal dominant trait. Phenylthiourea contains the N–C=S group on which the taste peculiarity apparently depends; goitrogenic or antithyroid substances (thiourea and thiouracil), which also contain this group, possess the same property with respect to taste.
See: taste deficiency
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Examples: glitazone, GI cocktail, etc.