PRL and Cluster headache: Besides playing an essential role in several physiological processes, PRL is associated with different pain conditions, including: postoperative [78], inflammatory [14, 79], neuropathic [14] and orofacial pain [80], as well as primary (i.e. migraine and cluster headache) and secondary headaches (i.e. prolactinoma- and/or pituitary diseases-associated headaches) [6, 12, 14–17].