Pituitary tumours

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Pituitary tumours


Epidemiology and pathology


Pituitary tumours are common, and the most common are prolactinomas with an incidence of up to 1 in 3000 of the population per annum. Pituitary tumours arise from the anterior lobe and produce their effects by uncontrolled production of specific hormones, by destruction of normal pituitary tissues, leading to hypopituitarism or by compressing adjacent structures such as the optic chiasm, hypothalamus and bony structures (Table 24.1). Secretory tumours produce syndromes that cause gross clinical signs and symptoms. The local symptoms include headaches and visual field loss. The systemic symptoms produced depend upon the secreted product and range from acromegaly to pituitary Cushing’s disease.


There are no classical oncogene mutations in pituitary tumours. However, there are clues to the development of this group of malignancies that come from dysregulation of the inhibitory components of the β-catenin pathway, and the relationship of this pathway to the cadherins. Both the Akt and MAPK pathways appear to be overexpressed in many pituitary tumours, and this blocks the inhibitors of the cell cycle. This is equivalent to snapping the brake cable as you are bicycling down a steep hill. The role of epigenetic modulation of gene expression in the aetiology of pituitary tumours is a cause for considerable excitement in endocrinologists, but oncologists have remained calm because in their view there is a lack of specificity to the changes described.


Treatment


Treatment options for pituitary tumours include blocking agents, such as bromocriptine and other dopamine agonists, neurosurgery and radiotherapy. The mainstay of therapy, however, is surgery, which is important in establishing the histological diagnosis, in decompressing the optic chiasm and in relieving obstructive hydrocephalus, as well as providing the possibility for completely excising the tumour. A transfrontal approach is required for large tumours with extrasellar extension, while for smaller tumours a trans-sphenoidal approach with dissecting microscope to the fore is safer and tolerated better. Radiotherapy may be used as the primary treatment for intrasellar tumours and as an adjunct to surgery for larger tumours. Surgery is more likely to control pituitary tumours than radiotherapy. The outlook is generally excellent with 5-year overall survival rates in excess of 85%.



Table 24.1 Comparison of clinical features of pituitary tumours














































Tumour Percentage of tumours Morphology Endocrine features Neurological features
Prolactin-secreting adenoma 40 Macroadenoma Amenorrhoea, galactorrhoea, hypopituitarism in men Headache, visual field defects
Non-secretory adenoma 20 Macroadenoma Hypopituitarism Headache, visual field defects
Growth hormone-secreting adenoma 20 Macroadenoma Gigantism in children, acromegaly in adults Headache, visual field defects
Corticotrophin-secreting adenoma 15 Microadenoma Cushing’s disease Usually none
Gonadotropin-secreting adenoma 5 Macroadenoma Panhypopituitarism Headache, visual field defects
Thyrotropin-secreting adenoma <1 Microadenoma Hyperthyroidism Usually none

In the treatment of pituitary Cushing’s disease, where first-line therapies have failed and disease progression on first-line agents such as bromocriptine has occurred, the role of alternative agents blocking metabolic pathways becomes important; metyrapone, ketoconazole, mitotane and etomidate all inhibit enzymes involved in steroid synthesis and are used. Additionally drugs that affect ACTH production including the dopamine receptor D2 agonist cabergoline and the somatostatin analogue pasireotide are occasionally used with some benefit.


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Case Study: The infertile banker with a headache.

Oct 9, 2017 | Posted by in ONCOLOGY | Comments Off on Pituitary tumours
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