Among them, the most important are: (i) the disappearance of cortisol circadian rhythms in many malignant tumors; (ii) abnormally high levels of prolactin; and, in particular, (iii) pineal endocrine deficiency or a progressive decline in the nocturnal melatonin production that represents the main and the most investigated cancer-progression-related neuroendocrine alteration [97]. The gene discussed is PRL; the disease is cancer.