The role of the hypothalamo-pituitary axis in headache
This thesis investigates the hypothesis that dysfunction of the hypothalamo-pituitary axis is important in headache in patients with pituitary disorders. The observation that patients with small functional pituitary tumours may suffer with severe headache syndromes, and the dramatic analgesic effect that may be seen with somatostatin analogues, are central to the thesis. In the first study, I showed that there was no correlation between pituitary volume or cavernous sinus invasion with headache in pituitary tumours. In this study, prolactinomas and growth hormone- secreting tumours were found to be associated with the highest degree of headache, suggesting that biochemical mechanisms may be more important than structural ones in the pathophysiology of pituitary tumour-associated headache. In the second study, the presence of potentially nociceptive peptides CGRP and substance P within pituitary tumours was investigated there was no association between the presence of these peptides and headache. In the third study, the clinical characteristics of pituitary tumour-associated headache were investigated. The commonest presentation of headache was migraine. The rare primary headache, Short lasting Unilateral Neuralgiform headache attacks with Conjunctival injection and Tearing (SUNCT), was exclusively associated with acromegaly or prolactinoma. In the fourth study, the possibility that cessation of somatostatin infusion could be a useful non-vascular way of triggering headache was investigated the headache induction was not reliable. In the final study, the potential use of octreotide in the management of primary headache was investigated. Octreotide was unhelpful for migraine, but was efficacious in the acute treatment of cluster headache. The findings suggest that functional disturbances in the hypothalamo-pituitary axis may have a pathophysiological role in some headache types.