A model for LHβ promoter repression by a physical interaction between AR and SF-1. (After Jorgensen and Nilson, Ref. ) In the presence of elevated androgen concentrations, AR (androgen receptor) interacts with SF-1 on LHβ promoter, preventing interaction of Egr-1 with its response elements. LHβ is then turned off. A GnRH pulse (resulting from a reduction in circulating androgen concentrations), favours Egr-1 transcription, increasing its accumulation. In turn, Egr-1 displaces AR from SF-1 and favours an active setting of transcription factors on LHβ promoter. LHβ transcription is then triggered. The resulting LH protein production in turn stimulates androgens production by the gonads.