Estrogen and chronic daily headache.

Estrogen exerts a strong influence on episodic headaches, such as migraine and tension-type headache. A relationship between sex hormones and chronic daily headache (CDH) is less well established. However, similarities between episodic and CDH suggest that estrogen also may significantly influence CDH. Pathophysiologic studies of CDH identify neurochemical abnormalities similar to those influenced by estrogen in episodic headache, such as aberrant 5-hydroxytryptamine activity. In addition, gender differences in CDH prevalence in pediatric and adult populations support a hormonal influence. Few studies have evaluated the ability of gynecologic events, such as menses, to influence CDH.