“Ask Dr. HKSH” - Pituitary Tumours

Dr. LEUNG Kar Ming

Specialist in Neurosurgery

1. What is the pituitary gland? What is its function?

The pituitary gland is an endocrine organ in the brain that regulates hormone secretion. It is situated deep inside the skull and behind the nose. The pituitary gland measures only a few millimetres in size and is located directly below the optic chiasm, at which the optic nerves from each eye cross, with the internal carotid arteries lying adjacent on both sides. These two internal carotid arteries are the main blood supply to the brain. The primary function of the pituitary gland is to regulate secretion of hormones such as cortisol, thyroxine, and growth hormone. All of these hormones are controlled by the pituitary gland. Even the body fluid balance, which relates to how much we drink and urinate, is also regulated by the pituitary gland.

2. What are the types of pituitary tumours?

Pituitary tumours can be classified in two ways. Firstly, they can be categorised by size. Tumours smaller than 1cm are called microadenomas, those larger than 1cm are classified as macroadenomas. Pituitary tumours can also be classified by their secretory function: functional or non-functional types. Non-functional tumours do not secrete abnormal hormones, and therefore patient will not have clinical features from hormonal disturbance. For functional tumours, the most common type is prolactinoma, other less common types may also cause excessive secretion of hormones, such as Cushing’s disease, in which there is abnormally high level of cortisol, and acromegaly, gigantism where growth hormone is in excess.

3. What are the symptoms of pituitary tumours? What diseases are they associated with?

The tumour will compress on surrounding tissues when it grows. The pituitary gland is situated just beneath the optic chasm (confluence of optic nerves from both eyes). When the tumour enlarges and compresses on the optic nerves and chasm, the patient will have restricted visual field on both sides. When there is further compression from tumour growth, vision will be further impaired.

At a later stage, patients may experience headaches from increased intracranial pressure. An advanced tumour may even press upon the ventricles and disrupt cerebrospinal fluid circulation, causing hydrocephalus.       

In addition to mass effect, tumours can affect patient’s physiological function. As mentioned earlier, excess prolactin can cause reduced menstruation or even amenorrhoea in women, which can lead to infertility. On the other hand, prolactin stimulates breast tissue proliferation. For women with prolactin-secreting tumours, elevated levels of prolactin can cause breast swelling and milk secretion even in absence of pregnancy. Male patients may experience sexual dysfunction and breast enlargement. Risk of osteoporosis may also be increased if prolactin level remains abnormally high for long period of time.

Another condition is Cushing’s disease, where excessive cortisol secretion resulting in numerous complications, such as resistant diabetes, hypertension, and central obesity. The face and trunk may become obese out of proportion to the limbs. The skin may become thin and fragile, with purple striae. The abnormal blood pressure and glucose metabolism will subsequently lead to cardiovascular complications.

Another rare condition is acromegaly and gigantism, caused by growth hormone-secreting tumour. Soft tissue in the body gradually enlarges in the presence of excessive growth hormone. Patients will notice that their shoe size is getting larger and larger, and their fingers can no longer fit in their usually worn rings.

Other features that gradually appear include coarse skin, prominent eyebrows, broadened nose, and widening of interdental spaces. In some patients, the voice may become deepened, and women may have coarse facial features. Blood pressure and blood glucose may also become more difficult to control, and need ever-higher dose of diabetic and anti-hypertensive medications.

On the other hand, normal secretory function may be deficient when the functioning glandular tissue is compressed by the tumour. Patient will have symptom when there is insufficiency of hormone like cortisol or thyroxine. Patients will have excessive malaise despite long sleeping hours. They may also have cold intolerance, loss of appetite, and constipation. In more severe situations, blood pressure may remain persistently low, along with heart rate, and fail to rise in stressful or critical situations. They may even run into shock condition.

4. How is a pituitary tumour diagnosed?

Doctor will ask specifically about one’s medical history and arrange comprehensive examinations to look for any visual field defect and relevant signs. Blood tests are also conducted to detect any abnormal hormonal levels. Brain scan, mostly MRI, is performed to confirm the diagnosis.

5. How is a pituitary tumour treated? Is surgical removal mandatory?

Management strategy depends on nature and size of the tumour. Non-functional microadenoma is usually observed unless it shows progressive enlargement. Prolactinoma is treated with medication, which can control or even normalise the prolactin level. In some situation, the tumour may shrink or even resolve completely. However, when the tumour grows and compress on the optic nerves or brain tissue, surgical removal is needed.

Minimally invasive trans-sphenoidal tumour resection is currently the most common surgical option. This procedure involves accessing the pituitary gland at the sella turcica via the posterior nasal cavity and sphenoidal sinus. The sella turcica is a bony depression at the central of skull base where the pituitary gland is located. Under endoscopes or microscopes, a small opening is created in the sella turcica to remove the pituitary tumour.

Most of these tumours are as soft as viscous liquid. So they can be curetted or sucked out with instruments via a small incision. The greatest challenge of this surgery is to avoid causing injury to the adjacent blood vessels and prevent haemorrhage. Therefore, if the tumour is close to or adhering to blood vessels, the portion will be left behind.  As the vast majority of these tumours are benign, small residual can be observed. If the residual portion is substantial or it shows signs of early recurrence, stereotactic radiosurgery can often be used as adjunctive treatment.

6. How long does it take to recover after surgery?

Generally, patients are expected to stay in hospital for about one week after pituitary surgery for monitoring of wound healing, and assessment of hormonal levels. Replacement therapy can be started if there is hormonal insufficiency. If the condition is stable after one week, patients can be discharged and resume usual daily activities.