STPM Biology - chapter 11: Revision essay question 3

3. Target cells of a hormone will often reduce the number of receptors for a hormone when the levels for that hormone become chronically elevated.  Conversely, the number of receptors for a hormone may increase if the concentration of a hormone is chronically reduced.  Explain why this occurs during these cases. 
 
Answer

Hormones are chemical messengers that are required in small quantities to produce their effects.  If hormone levels are elevated for long periods of time, cells with the correct receptors will only need a smaller number of receptors for maximum response.  Therefore, the cell has more receptors for this hormone than it needs and will respond by reducing the number of receptors.  Conversely, if tissue fluid levels, including blood, of hormones are chronically low, cells will produce more receptors to maximize their response to existing levels of hormones.   

Assignment submitted by Dhevan, 2011/2012(IBM)