The early phase during which the stroma is actively replicating and expanding is characterised by expression of some genes related to PCOS, including FBN3, LHCGR and GATA4. In an intermediate stage the expression of stromal genes suggests that it has matured to express structural collagens and fibrillins associated with adult tissues, and under the control of TGFβ signalling and perhaps androgens. The gene discussed is TGFB1; the disease is polycystic ovary syndrome.