What can go wrong with the Pituitary Gland?
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:
- They can over-produce a pituitary hormone
- They can cause inadequate production of other remaining pituitary hormones
- They can cause problems by local effects on anatomically related structures.
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).
- Visual pathways - interference with these pathways will result in visual disturbances
- The cavernous sinus - this houses cranial nerves (III, IV & VI) which are important in eye movements
- The meninges - pressure on the meninges usually presents with headache
- The third ventricle - pressure on the ventricles can lead to interuption of the flow of cerebrospinal fluid (CSF) and can lead to hydrocephalus
- The hypothalamus - any damage to the hypothalamus can manifest in a number of different ways from altered thirst to precocious puberty
- The sphenoid sinus - downward extension of the tumour into the sphenoid sinus can lead to CSF leaks and nasal obstruction.
Other problems that can affect the pituitary are isolated deficiencies in any of the pituitary hormones, a phenomenon known as hypopituitarism.