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We conclude that the decrease with age of corticosteroid receptors is possibly related to a physiological involution of corticosteroid receptors and that this reduction does increase plasma cortisol concentration, without affecting the glucocorticoid effector mechanism .
 corticosteroid receptors, corticosteroid receptors
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 corticosteroid receptors, corticosteroid receptors