The pituitary gland is a small oval-shaped endocrine gland located at the base of the brain just behind the nose and below the optic nerve (the nerve which leads to the eyes). It is about the size of a pea and is very important because it secretes several chemical messages known as hormones.
Hormones produced by the pituitary gland helps to regulate and control the secretion of hormones from other endocrine glands which are responsible for the body’s growth, metabolism and maturation.
What is a Pituitary Tumour?
Generally, pituitary tumours are benign (non-cancerous) and slow growing. Pituitary tumours constitute 10% of primary brain tumours. Pituitary tumours are either secreting (producing hormones) or non-secreting tumours (not producing hormones). Both categories may press on structures around the pituitary fossa e.g. the optic nerve.
It is caused by direct pressure from the tumour itself. As the tumour grows, it puts pressure on the optic nerve, which often caused blurring vision.
It results in amenorrhoea (no menstruation), cold intolerance, general weakness, etc.
It happens to the younger group of patients before bones mature if the tumour produces excessive amount of growth hormone.
It causes enlargement of lip, hand and feet, also lead to high blood pressure and diabetes if the tumour produces excessive amount of growth hormone.
Moon face, weight gain, increase facial hair in women and mental changes
Excessive Adreno-Corticotrophic hormone (ACTH) stimulates the adrenal gland to make and secrete glucocorticoids. Excessive amounts of glucocorticoid hormones causes build up of fats in the face, neck, trunk, weight gain, increased facial hair in women and mental changes such as depression. Excessive amount of sugar (Diabetes Mellitus) and high blood pressure may occur.
Irregularity of menstruation, loss of sexual function, infertility and general weakness
Due to excessive production of prolactin, there may be irregular menstruation, inappropriate milk production by the breast (galactorrhoea) and infertility in women; impotence and infertility in men.
The cause of pituitary tumours, like that of other brain tumours, is unknown. It can occur in all age groups, but it is more common in middle and older age groups.
Diagnosis of pituitary tumours is by the following:
Surgical excision will allow accurate diagnosis of the type of tumour and relieve pressure on surrounding structures. The preferred surgery is the trans-sphenoidal approach where tumour is removed through the nasal passage via an incision in the mouth or nose.
Another approach is the craniotomy where a portion of the bone skull is removed to gain access to the tumour. The bone will later be replaced following the tumour’s removal.
Thyroxine and hydrocortisone tablets are the common drugs which help replace hormones deficiencies. Drug therapy may be lifelong treatment and must be continued even in sickness. Bromocryptine or Cabergoline is given when the tumour produced large amount of prolactin, as suppressing prolactin production may cause shrinkage of the tumour.
Pituitary tumours in patients unfit for surgery or those that extend beyond the pituary fossa require treatment by radiation. Radiation treatment is also an option for small pituitary tumours that do not compress the optic nerves. Radiation is carried out using the Novalis Shaped-Beam machine located at the NNI-Khoo Teck Puat Radiosurgery Suite at Singapore General Hospital (SGH) Level B1, Block 2 . This delivers narrow beams of strong radiation aimed precisely at the tumour from many different directions. Normal brain tissue therefore receives only a fraction of the total radiation dose received by the tumour. Exact knowledge of the tumour location is necessary, and this is achieved by securing the head firmly but painless in a custom-made mask system and doing a CT scan of the head with the mask system in place. For treatment planning, an MRI scan of the head is also required.
It is very important to visit your doctor regularly for follow up with laboratory tests of hormone levels and imaging studies e.g. MRI. If recurrence is diagnosed, further treatment may be necessary. Large recurrence may require radiation therapy and/ or drug therapy as well.