Abstract
SUMMARY: The role of mechanical forces influencing the growth of a pituitary adenoma is poorly understood. In this paper we report the case of a young man with hyperprolactinaemia and an empty sella secondary to hydrocephalia, who developed a macroprolactinoma following the relief of high intraventricular pressure. LEARNING POINTS: The volume of a pituitary tumour may be influenced not only by molecular but also by local mechanical factors.Intratumoural pressure, resistance of the sellar diaphragm and intracranial liquid pressure may play a role in the final size of a pituitary adenoma.The presence of hydrocephalus may hide a pituitary macroadenoma.