[en] A current research topic, that is developed in this presentation, is the study of disturbance of circadian hormonal cycles and the secretion of melatonin. Traumatic brain injury is associated to hypopituitarism in up to 10-35% of cases, depending on the dynamic tests used to diagnose hypopituitarism (Valdés-Socin & al 2009, Valdés-Socin & al 2015).Melatonin secretion and hormonal rhythms are severely disturbed in acute TBI patients (Seifman & al. Front Neurol 2014).Light is the primary variable that entrains the main circadian clock in the central nervous system. The retinohypothalamic tract generates an overt 24-hour rhythm. These coordinated outputs are conveyed through to the rest of the body via neuroendocrine (ie melatonin and ACTH-cortisol secretion), autonomic (sympathetic and parasympathetic pathways) and behavioral pathways (feeding, locomotor activity, etc).Finally, we will discuss some recent data connecting light pollution and nocturnal human activity with the metabolic syndrome (chronobesity).