When a hormone is present in excessive levels, the number of target-cell receptors my decrease. This is called . A. Receptor recognition B. Paracrine regulation C. Sensory adaptation D. Up-regulation E. Down-regulation

E. Down-regulation

Explanation:Cells typically up or down  regulate  depending on  the concentration of a hormone levels. When  there is a excessive  concentration of a hormone in the blood stream, the cell decreases the number of receptors reducing  the interaction  with that hormone, Also, when there is excessive  hormone reduction, the  target cells activate to increase their number of receptors.

Down  regulation occurs by the the deactivating or degrading of target cells to reduce the number of  receptors due to their sensitivity to a particular excess hormone.

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