Other hormone receptors or signalling molecules that could be investigated are chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII), heart and neural crest derivatives expressed 2 (HAND2) and steroid receptor coactivator-1 (SRC-1), which are related to progesterone and estrogen signalling in endometriosis [89]. The gene discussed is TCEA1; the disease is endometriosis.