Hypothalamic damage, particularly in the posterior region, can lead to hypothermia (cf. hyperthermia) or poikilothermia (body temperature varying with ambient temperature, as in reptiles). There are many pathological causes, including tumor, trauma, infarct, hemorrhage, sarcoidosis, Wernicke’s encephalopathy, fat embolism, histiocytosis X, and multiple sclerosis (rare)
A rare syndrome of paroxysmal or periodic hypothermia has been described, and labeled as diencephalic epilepsy. Nonneurological causes of hypothermia are more common, including hypothyroidism, hypopituitarism, hypoglycemia, and drug overdose.
Thomas DJ, Green ID. Periodic hypothermia. BMJ 1973; 2: 696-697