Management of pituitary tumours: strategy for investigation and follow-up.

Abstract

Investigation of a patient presenting with evidence of a pituitary tumour has three main objectives: investigation of any hormonal hypersecretion; assessment of residual pituitary function, and examination of any mass effect of the tumour. A prolactin-secreting adenoma is often easily diagnosed by performance of a basal prolactin level. Biochemical assessment to exclude acromegaly or Cushing's disease should only be performed if clinically indicated. The standard investigations for acromegaly consist of establishing the degree of growth hormone (GH) suppression following a glucose load and estimating the basal insulin-like growth factor-I level. Before detailed investigation for Cushing's disease is initiated, the presence of Cushing's syndrome must be established. The second requirement is to determine the presence of any pituitary hyposecretion. Whilst the remainder of pituitary function can be assessed by baseline hormonal estimations, the evaluation of ACTH and GH secretion necessitates dynamic function testing. Lastly, the impact of the mass itself requires careful examination. Both neuroradiology, preferably magnetic resonance imaging at a centre specialized in examination of the pituitary fossa, and careful detailed clinical examination of the visual fields should be performed. The follow-up requirements in an individual patient are affected by a number of factors including the size and nature of the underlying tumour and any treatment administered. In patients with a hormone-secreting tumour, the hormone levels themselves provide a 'tumour marker' to aid follow-up. An important caveat, however, is that on some occasions tumour size and hormone levels do not change in parallel. Patients who have undergone pituitary surgery should have dynamic assessment of pituitary function performed approximately 6 weeks after surgery. There is no reason to suspect any further impairment of pituitary function after this date. In direct contrast, pituitary hormone deficiencies after radiotherapy are unlikely less than 6 months after treatment. Patients should undergo testing of pituitary reserve at 6 months, and then at yearly intervals for at least 10 years after radiotherapy, if they have not already developed panhypopituitarism. Even after this period, if patients develop new symptoms the possibility of further pituitary hormone deficits should be considered. Neuroradiology should be performed approximately 6 weeks to 3 months after surgery. If radiotherapy is not administered, neuroradiology should be performed yearly for at least 10 years. If the patient has received radiotherapy, tumour recurrence is much less likely and therefore in these individuals neuroradiology does not need to be performed with such regularity. In conclusion, when planning the investigation and follow-up of an individual patient, one should take into account the size and characteristics of the tumour, as well as the treatment modalities.