Current research in biomedicine is still mostly based on purely experimental discoveries while modelling and simulation are almost unused. Systems biology and systems medicine try to improve the situation, how-ever, mathematical models are being treated in similar manner as biological models, therefore, their contribution is still limited. In this article we show a simplified model of cholesterol metabolism in the body and ana-lyse its properties with respect to system dynamics. Cholesterol metabolism system shows high robustness on metabolic level, while gene expression regulation is susceptible to external disturbances. The model suggests that it is possible to push similar metabolic systems to alternative stable equilibrium point and cause severe problems (disease) without actually damaging the struc-ture of any of the involved molecular species. This new concept of disease understanding my help solve many disease treatment problems.