The tumours that arise are in the anterior pituitary and are:
The remaining 12% are non-functioning tumours.
The excess prolactin produced results in production of milk (galactorrhoea) and absence of periods (amenorrhoea) in women. In men, it causes impotence and infertility. Medical treatment consists of bromocriptine treatment. Surgery is done where possible by performing a transphenoidal hypophysectomy (where the affected part of the pituitary is removed by an operation performed through the nose).
Excess growth hormone causes gigantism in children (where their long bones increase quickly in length) and acromegaly in adults. Acromegaly is a syndrome characterised by increased bone and cartilage growth, enlargement of the heart and associated abnormalities, enlargement of other organs, diabetes mellitus, decreased functioning of the gonads (hypogonadism) and colonic polyps with associated risk of colonic cancer. This is all dealt with in detail in the Pituitary section.
Transphenoidal surgery is again the treatment of choice. Octreotide may be used to control symptoms. Radiotherapy is also used.
Excess ACTH from the pituitary causes overstimulation of the adrenal gland, causing it to produce too much cortisol. This then produces the characteristic Cushing's syndrome (see 'Adrenal' section). This produces obesity, thin skin with bruising, muscular weakness, high blood pressure (hypertension), menstrual irregularity in women, psychological disturbance, osteoporosis and increased rate of infection with poor wound healing.
Again this is best treated by transphenoidal surgery to remove the pituitary tumour. Drug treatment with ketoconazole can be used to reduce symptoms whilst awaiting tests and surgery. Pituitary radiotherapy is also another option.
For much more information on pituitary tumours and pituitary physiology please see the relevant parts of the 'Pituitary' section of this website.