The most common cause of pituitary disease are pituitary tumours. Pituitary tumours represent 12.5% of all intracranial neoplasms and over 99% are benign tumours known as adenomas. These tumours can cause problems in a number of ways:
75% of the adenomas are endocrinologically active, with prolactin-producing adenomas (prolactinomas) being the most common (approximately 40%). These tumours can either be microadenomas (less than 10mm in diameter) or macroadenomas. Growth-hormone producing adenomas produce acromegaly, and are thought to account for around 20% of the endocrinologically active adenomas. 10% of the overall group are thought to secrete both growth hormone and prolactin. 15% of the group secrete cortiocotrophin that produces Cushing's disease. Thyrotrophin and gonadotrophin secreting tumours are much rarer and account for about 1% each of the group.
The other 25% of the adenomas are known as chromophobe or null cell adenomas. These adenomas are not endocrinologically active and produce symptoms by interfering with their anatomical relations. The most important anatomically related structures are listed below (with the symptoms they produce when interfered with).
Other problems that can affect the pituitary are isolated deficiencies in any of the pituitary hormones, a phenomenon known as hypopituitarism.