Macotela et al. presented the concept of moderately elevated PRL levels as a part of a homeorhetic response to either physiological (e.g., pregnancy, lactation, stress) or pathological (e.g., obesity and MS) metabolic challenges, allowing a series of metabolic adaptations to deal with physio-pathological demand [27]. The gene discussed is PRL; the disease is obesity due to melanocortin 4 receptor deficiency.