Chapter 1 general introduction This chapter includes a description of the ana-tomy of the pituitary gland, the prevalence and the various treatment modalities of pituitary adenoma, as well as the side-effects of treatment.
The pituitary gland plays a central role in hormone production and hormone regulation in the human body. Pituitary adenomas account for at least 12% of all intracranial neoplasms with an incidence of 20 to 30 per million per year. Almost all pituitary adenomas are benign tumours. Approximately 25% to 30% of the pituitary adenomas do not result in hormonal overproduction and these adenomas are generally referred to as non-functioning pituitary adenomas (NFA). In the absence of hormonal excess patients present with symptoms due to mass effect of the NFA such as compression of the optic apparatus, resulting in loss of vision. Furthermore, pituitary hormone secretion may be impaired. Age at diagnosis is generally between 40 and 50 years.
Hypersecretory pituitary adenomas account for 70% to 75% of the pituitary ade-nomas.
These tumours may produce the following hormones in excess:
• growth hormone (GH); GH hypersecretion manifests as acromegaly in adults and gigantism in adolescents, and results in growth of many anatomical structures of the human body.
• adrenocorticotrophic hormone (ACTH); ACTH excess manifests as Cushing’s di-sease.
• prolactin (Prl); Prl excess results in galactorrhoea in women and reduced fertility in men and women.
In general, patients with hypersecretory adenomas present at a younger age in comparison with patients with NFA and these adenomas are usually smaller.
Neurosurgery is in most cases the treatment of choice for NFA, GH- and ACTH-
secreting adenoma in order to decompress the neighbouring anatomical structures of the pituitary adenoma and/or to reduce hypersecretion of hormones.
In case of prolactinoma and residual disease after neurosurgery among patients with a GH- and ACTH-secreting adenoma, treatment with hormone-suppressing medication relieves symptoms and adverse metabolic consequences.
Radiation therapy, in most cases applied postoperatively, results in long-term local control and improvement of hormonal hypersecretion.
Possible side-effects of radiation therapy are used as argument to postpone or reject radiation therapy in residual pituitary adenomas. These side-effects are discussed and are placed in perspective to the adverse consequences of local extension of the pituitary adenomas itself, the neurosurgical procedures and the effects of sustained medication. In addition, the use of more advanced and emerging radiation delivery techniques will further reduce the probability of radiation-
induced side-effects.