Thus, mice harbouring a transgene with the SV40 early gene encoding large T antigen ligated to the POMC promoter, developed melanotroph tumours (Low et al., 1993), and mice harbouring the SV40 T antigen targeted to gonoadotroph cells using the follicle stimulating hormone β (Fshβ) promoter, generated a model of non-functioning adenomas (Kumar et al., 1998). The gene discussed is POMC; the disease is adenoma.