LEP and obesity due to melanocortin 4 receptor deficiency: The relationship between obesity, leptin and breast cancer has taken a further slope, that of chemotherapy resistance mediated by adipokines, proteins released by adipose tissue and can be involved in the action of chemotherapeutic drugs, since the higher risk of recurrence and mortality in patients with obesity and breast cancer could be related to a lower efficacy of cancer treatments, this is probably due to the plasma variations of adipokine levels, since women with breast cancer and obesity are less sensitive to chemotherapy and have higher mortality rates7.