Pituitary Tumours Diagnosis & Treatment

What is The pituitary gland?

The pituitary gland is a small structure, about the size of pea, located in the middle of the head just under the brain to which it is attached by the pituitary stalk. For its size, it has an impressive array of important endocrine (hormonal) functions.

It secretes a large number of hormones into the blood which in turn control numerous important body functions.

Thyroid stimulating hormone (TSH) stimulates the thyroid gland to secrete the thyroid hormones. The thyroid hormones control body metabolism.
Adrenocorticotropic hormone (ACTH) is an important hormone that stimulates the secretion of cortisol from the adrenal glands. These are important for maintaining basic body functions including immunity, blood pressure as well as the body’s response to stress.
Follicle stimulate hormone (FSH) and Luteinising hormone (LH) regulate function of the ovaries in women and testes in men, and are important for production of oestrogen and testosterone.
Growth hormone (GH) stimulates growth of the body.
Prolactin stimulates the secretion of breast milk.

Oxytocin and antidiuretic hormone (ADH) are also released by the pituitary gland. However, these are produced by another region of the brain called the hypothalamus, travel through the pituitary stalk and are released by the posterior pituitary gland. They are not produced by pituitary adenomas.

Pituitary adenomas

Some people develop tumours of the pituitary gland. These tumours are called pituitary adenomas. They are almost always benign. They are classified in terms of size as either a macroadenoma (>10 mm) or a microadenoma (<10mm).

They are also classified on the basis of whether they secrete a particular hormone or whether they are non-secretory. Those that secrete certain hormones are further classified on the basis of the hormone that they secrete.

What are the symptoms of a pituitary tumour?

The symptoms of a pituitary tumour depend on the size of the tumour and whether the tumour secretes certain hormones.

Large tumours may cause symptoms on the basis of the hormones it secretes as well as pressure on the surrounding structures. The main surrounding structures include the normal pituitary gland and the optic chiasm.

The function of the surrounding normal pituitary can be impaired by the pituitary tumour as it becomes compressed. Patients can develop hypopituitarism. This is very common in large nonsecretory pituitary adenomas and is often associated with generalized fatigue and being unwell. They may have features of hypothyroidism and men often have features of low testosterone including sexual dysfunction and loss of libido. Patients respond well to hormone replacement.

The optic chiasms is located just above the pituitary gland. The optic chiasm is where the optic nerve from each eye joins together with some fibres within each nerve crossing to the opposite side. The pituitary gland sits in the pituitary fossa or sella. This is a bony hollow in the base of the skull hence the pituitary gland is surrounded by bone except above. As such, large adenomas grow upwards and can compress the optic chiasm which can lead to a loss of vision. The pattern of vision is a loss of visual field on each side called a bitemporal hemianopia. It can become permanent.

Small tumours (microadenomas) may also produce significant symptoms if the tumour secretes large amounts of certain pituitary hormones.

For example, Cushing’s Disease is caused by a hypersecretion of ACTH. This is a type of Cushing’s Syndrome caused by a pituitary tumour. As a result of the increase in ACTH secretion, a patient will have abnormally high levels of cortisol which will cause obesity, muscle weakness, bruising and striae of the skin, and fatigue.

Pituitary apoplexy is a serious condition where a bleed or haemorrhage occurs within the pituitary gland. This is usually associated with a pituitary tumour. It is characterized by sudden onset of severe headache. Patients are generally unwell due to acute pituitary insufficiency. This requires acute medical management and often requires surgery.

How are pituitary tumours managed?

Pituitary tumours are normally diagnosed on the basis of an MRI scan of the pituitary. However, patients require careful clinical assessment of both their endocrine status but also, particularly in large tumours, their vision.

Apart from clinical assessment through history and examination, a range of blood tests called pituitary functions tests will be performed to assess whether the pituitary gland is under or over producing various pituitary hormones. An endocrinologist will be an essential member of the clinical team in managing patients with pituitary tumours.

Some tumours that secrete excess hormones can be treated medically. Prolactinomas are pituitary adenomas that secrete excessive prolactin. This can result in a range of symptoms including galactorrhoea, that is, milk production from the nipples. While many large pituitary tumours will produce a modest increase in prolactin secretion called the ‘stalk effect’, prolactinomas result in very high levels of prolactin. They can often be treated medically with marked reduction in the adenoma. This can often avoid surgery.

Patients that are deficient in some hormones will need hormone replacement. Patients with hypopituitarism will often need thyroid hormone replacement. Men will often need testosterone replacement.

Patients with larger tumours that compress the optic chiasm or optic nerves will require formal ophthalmological assessment including visual field testing. Loss of peripheral vision due to optic nerve compression can produce what is termed bilateral temporal hemianopia. This can significantly impact vision and some patients with pituitary tumours can present with this as their primary symptom. Other patients may not be aware that they have lost peripheral vision until they are tested.

Large pituitary tumours and some hypersecretory microadenomas require surgery. Surgery is almost always performed through an endoscopic transnasal transsphenoidal approach. This is performed in conjunction with an ENT surgeon.

What type of surgery is performed for pituitary tumours?

The endoscopic transnasal transsphenoidal approach to a pituitary tumour involves using a telescope and specialised instruments to remove bone at the back of the nose to expose the pituitary tumour. An ENT surgeon with specialized training in these techniques performs the approach to allow Prof Owler to access the tumour. The tumour is then gently removed using small, specialised curettes. During surgery a specimen is sent for histological analysis to confirm the diagnosis of a pituitary adenoma.

What happens after surgery?

Following surgery patients are closely monitored during their hospital stay for any problems such as CSF leakage or hormone dysfunction. Patients are normally given a steroid medication which is then gradually weaned. Further tests of hormone function and, in particular, cortisol production, are performed. An MRI is also normally performed prior to discharge.

A follow-up appointment is scheduled with Prof Owler 6 weeks after surgery. Follow-up appointments are normally also made for review by the ENT surgeon and endocrinologist.

In the long term, MRI scans are repeated on a regular basis. These are reviewed with Prof Owler normally on an annual basis. Regular endocrine reviews are also usually scheduled.