In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.

 To explain the end - organ resistance to cortisol , the glucocorticoid receptors ( GR ) in peripheral mononuclear leukocytes and cultured skin fibroblasts from a forearm skin biopsy were characterized and compared with the results of similar studies in normal subjects .

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
glucocorticoid receptors