The metabolic headaches.

This review discusses headaches secondary to disorders of homeostasis, formerly known as "headaches associated with metabolic or systemic diseases." They include the headaches attributed to 1) hypoxia and/or hypercapnia (high altitude, diving, sleep apnea); 2) dialysis; 3) arterial hypertension; 4) hypothyroidism; 5) fasting; and 6) cardiac cephalalgia. For each headache type, we discuss the clinical features and diagnosis, as well as therapeutic strategies.