Medical management of functioning pituitary tumours

W Drake

St Bartholomew’s Hospital, London

Endocrine Nurses Training Course 10-12 September 2003
St Aidan's College, University of Durham, Windmill Hill, Durham DH1 3LJ

Most (~70%) anterior pituitary tumours are associated with a typical clinical syndrome, on account of excess secretion of a particular hormone. The remainder (~30%) tend to present with symptoms related to compression of nearby structures (e.g. the optic chiasm), with symptoms of pituitary failure, or they are discovered during radiological investigation for an unrelated symptom. Patients with functioning tumours may also have symptoms/signs related to the mechanical effects of the tumour, but it is usually the consequences of hormone excess that prompt them to seek medical attention.

Each of the anterior pituitary cell types may form a tumour that over-secretes its hormone. In practice, however, prolactinomas are easily the most common, followed by GH and ACTH secreting tumours. TSH and gonadotrophin secreting tumours are exceedingly rare and will not be discussed here.

The mainstay of management for prolactin secreting tumours is with dopamine agonist therapy (bromocriptine or cabergoline). In fact, these drugs are so successful that only a small minority of patients will require surgery or radiation treatment. Trans-spenoidal surgery remains the treatment of choice for patients with GH or ACTH secreting tumours, but a substantial proportion of patients will not be cured by surgery alone for each of these tumour types. In the case of acromegaly, this is because many patients present with large macroadenomas that cannot be completely resected. By contrast, most patients with ACTH secreting pituitary tumours (i.e. Cushing’s disease) have very small tumours that cannot easily be located. Options for medical therapy in acromegaly include dopamine agonists, somatostatin analogues (e.g. octreotide and lanreotide) and, shortly, the growth hormone receptor antagonist pegvisomant. For patients with Cushing’s syndrome drugs that inhibit cortisol synthesis include metyrapone, ketoconazole and, rarely, mitotane.

This talk will discuss the mechanism of action of many commonly used medical therapies for functioning pituitary tumours and detail many of the important side effects. In doing so, it is hoped that you will maintain and expand your role as invaluable information resource to patients with serious endocrine disease.

The opinions expressed in this paper are those of the speaker and do not necessarily reflect the views of the Society