What is the Pituitary Gland?
The pituitary gland, also referred to as the master gland because of its role in overseeing the other glands of the endocrine system and controls hormone levels. The pituitary gland is pea-shaped and located at the base of the brain. The pituitary gland is connected to the nervous system by a part of the brain called the hypothalamus.
What is a Pituitary Tumour?
A pituitary tumour (also known as a pituitary adenoma) is a mass of cells that grow on the pituitary gland. They are usually benign (not cancerous) and slow growing. Benign tumours do not spread to other parts of the body. Treatment may include surgery, radiation therapy and medication, or monitoring. Although the effects of pituitary tumours are understood, like many tumours, the causes remain largely unknown.
Symptoms of pituitary tumours
Often symptoms can be mild, non-specific and gradual in onset and may have different causes. Some symptoms can be caused by a tumour pressing on surrounding structures.
Symptoms may include:
- visual disturbances
- loss of libido (sex drive) or erectile dysfunction in men
- menstrual period irregularities in women
- changes to physical appearance
- cognitive difficulties
- persistent headaches
- nausea and vomiting
- light-headedness when standing up
Roles of the pituitary gland
The pituitary gland regulates many important bodily processes by releasing hormones into the bloodstream. Some of the key hormones include:
- Adrenocorticotropic hormone (ACTH) – stimulates the adrenal glands to produce the hormone cortisol, which is essential for life and helps to regulate blood pressure and blood sugar levels.
- Antidiuretic hormone (ADH) – helps the kidneys to maintain the correct amount of water in the body.
- Follicle stimulating hormone (FSH) and luteinising hormone (LH) – regulate the menstrual cycle in women, sperm production in men and sex hormone levels in both sexes.
- Growth hormone – influences a person’s height, contributes to bone and muscle building and influences the control of body fat.
- Prolactin – the main hormone for breast milk production, usually increased during pregnancy and with lactation.
- Thyroid stimulating hormone (TSH) – stimulates the thyroid gland to produce the hormone thyroxine, which regulates energy expenditure.
Types of pituitary tumours
The different types of pituitary tumour include:
- non-functioning pituitary tumour
- ACTH-producing tumour
- prolactin-producing tumour (prolactinoma)
- growth hormone-producing tumour.
Non-functioning pituitary tumour
This is the most common pituitary tumour and does not release any hormones. Symptoms are caused by a deficiency in the normal pituitary hormones (because the tumour restricts the function of the normal gland), or by pressure on surrounding structures near the pituitary.
Some of the symptoms of a non-functioning pituitary tumour include:
- general fatigue and feeling unwell
- persistent headaches
- menstrual cycle irregularities
- loss of peripheral vision
- loss of libido.
This type of tumour secretes adrenocorticotropic hormone (ACTH), which causes the adrenal glands (situated above the kidneys) to produce greater than normal amounts of cortisol. This causes a disorder known as Cushing’s disease.
Too much circulating cortisol may also occur due to non-pituitary influences, including adrenal gland tumours or other tumours outside the pituitary that make too much ACTH. These result in a clinical syndrome called Cushing’s syndrome.
The symptoms include:
- build-up of fat on the face (producing a ‘moon face’ appearance) plus a build-up of fat on the abdomen and upper back
- wasting of the arm and leg muscles
- high blood sugar levels
- a reddened, flushed face
- high blood pressure (hypertension)
- osteoporosis (thinning of the bones)
- thinning of the skin and easy bruising
- purple stretch marks.
This type of tumour releases prolactin, the hormone that naturally increases during pregnancy and after childbirth to stimulate milk production. A woman with a prolactin-producing tumour (prolactinoma) may have irregular or absent menstrual periods and her breasts may make milk, even if she isn’t pregnant.
The effects of this type of tumour in men include loss of libido and erectile dysfunction.
Growth hormone-producing tumour
This type of tumour releases growth hormone. Too much growth hormone forces certain body structures such as the face, hands and feet to enlarge and thicken considerably. This condition is called acromegaly, or gigantism if it occurs before growth stops during the adolescent years.
The cardiovascular changes caused by the high levels of growth hormone can be fatal if untreated. This condition also increases the risk of bowel polyps and cancer.
Diagnosis of pituitary tumours
A pituitary tumour is diagnosed using a number of tests including:
- medical history
- physical examination
- blood tests
- magnetic resonance imaging (MRI) scans
- computed tomography (CT) scans.
Treatment for pituitary tumours
Treatment depends on the type and size of the tumour, and the person’s age and general health. Generally, the treatment options include:
- Surgery – the pituitary gland is accessed via the nasal cavity and sinuses, and no visible cuts are made. The tumour is removed using an endoscope or microscope. In rare cases, the tumour may have to be removed through the front of the skull (craniotomy). Surgery is the first-line treatment for all tumours except prolactinomas and some larger tumours, making excess growth hormone that may be first treated with drugs.
- Radiation therapy – targets and destroys the tumour cells. Radiosurgery is focused radiotherapy that has improved the accuracy and minimised the risks of treating pituitary tumours. Radiosurgery is used in conjunction with surgery and medications to control the growth of tumours or to stop the activity of hormone-releasing tumours.
- Medication – to shrink the tumour and stop it from producing hormones. Medication is the first line of treatment for prolactinoma. Hormone replacement therapy may also be required in cases of pituitary hypofunction or post-operatively.
- Endoscopic transnasal transsphenoidal surgery
Surgical removal of a pituitary tumour usually is necessary if the tumour is pressing on the optic nerves or if the tumour is overproducing certain hormones. The success of surgery depends on the tumour type, its location, its size and whether the tumour has invaded surrounding tissues. The two main surgical techniques for treating pituitary tumours are:
- Endoscopic transnasal transsphenoidal approach. Endoscopes, thin telescopes with a camera and light, operating microscopes and specialised surgical instruments allow ENT and neurosurgeons to remove the pituitary tumour through your nose and sinuses without an external incision. This results in reduced operating time, less surgical damage, greater likelihood of surgical success, fewer complications and a faster recovery time.
- Transcranial approach (craniotomy). Large tumours may be difficult to remove via the nose, particularly if a tumour has invaded nearby nerves or brain tissue. These pituitary tumours are removed through the upper part of your skull via an incision in your scalp. Large, or more-complicated tumours are more accessible using this procedure.
Radiation Therapy for Pituitary Tumours
Radiotherapy is generally considered for patients with pituitary tumours who present with the following:
Post-operative scans demonstrate residual tumour outside the pituitary fossa
A pituitary tumour which re-grows after an extended period following surgery
A pituitary tumour, which continues to secrete a specific hormone following surgery, despite treatment with medication.
Radiotherapy describes the use of X-rays to treat pituitary tumours, and it works by damaging the DNA in the nucleus of any cells that it passes through.
It is important to note that many patients are not given radiation treatment after surgery and are followed up with yearly surveillance MRI scans, blood tests and visual field checks. However, it may not be possible for a neurosurgeon to remove the entire pituitary tumour, particularly a larger tumour, to minimise risk to surrounding structures, optic nerves or blood vessels. Small amounts of residual tumour have the tendency to slowly re-grow, even though a pituitary tumour is usually benign.
Types of radiation include:
- Stereotactic radiosurgery. Often delivered as a single high dose, this focuses radiation beams on the tumour without an incision. It delivers radiation beams the size and shape of the tumour into the tumour with the aid of special brain-imaging techniques. Minimal radiation comes in contact with healthy tissue surrounding the tumour, decreasing the risk of damage to normal tissue.
- External beam radiation. This delivers radiation in small increments over time. A series of treatments, usually five times a week over a four- to six-week period, is performed on an outpatient basis. While this therapy is often effective, it may take years to fully control the tumour growth and hormone production. Radiation therapy may also damage remaining normal pituitary cells and normal brain tissue, particularly near the pituitary gland.
- Intensity modulated radiation therapy (IMRT). This type of radiation therapy uses a computer that allows the doctor to shape the beams and surround the tumour from many angles. The strength of the beams can also be limited, which means surrounding tissues will receive less radiation.
Treatment with medications may help to block excess hormone secretion and sometimes shrink certain types of pituitary tumours:
Prolactin-secreting tumors (prolactinomas).
The drugs cabergoline and bromocriptine (Parlodel) decrease prolactin secretion and often reduce tumour size. Possible side effects include drowsiness, dizziness, nausea, nasal stuffiness, vomiting, diarrhoea or constipation, confusion, and depression. Some people develop compulsive behaviours, such as gambling, while taking these medications.
ACTH-producing tumours (Cushing disease).
The best treatment is surgery, but if there is residual or recurrent Cushing’s (which has been reported more than 25 years after initial surgery, hence the need for long term followup) then radiation or drug therapy may be needed. Drugs that may be used include cabergoline, pasireotide, ketoconazole, metyrapone, mitotane and mifepristone. All these drugs can have significant side effects and interactions with other drugs, so this will be all discussed with you and followed closely through your course of treatment.
Growth hormone-secreting tumours.
Two types of drugs are available for these types of pituitary tumours and are especially useful if surgery has been unsuccessful in normalising growth hormone production. One type of drugs known as somatostatin analogs, which includes drugs such as octreotide (Sandostatin) and lanreotide (Somatuline Depot), causes a decrease in growth hormone production and may shrink the tumour. These are given by injections, usually every four weeks. These drugs can cause side effects such as nausea, vomiting, diarrhoea, stomach pain, dizziness, headache and pain at the site of injection. Many of these side effects improve or even go away with time. They can also cause gallstones and may worsen diabetes mellitus. The second type of drugs, pegvisomant (Somavert), blocks the effect of excess growth hormone on the body. This drug, given by daily injections, may cause liver damage in some people.
Replacement of pituitary hormones
If a pituitary tumour or surgery to remove it decreases hormone production, you’ll likely need to take replacement hormones to maintain normal hormone levels. Some people who have radiation treatment also need pituitary hormone replacement.
Hormones that may need replacement are hydrocortisone, thyroxine, oestrogen or testosterone, and anti-diuretic hormone. These are all mostly tablets, although oestrogen can be given as patch or gel, and testosterone as spray, gel or injection, and anti-diuretic hormone as a spray. These will be reviewed regularly by the endocrinologist with blood tests initially daily after surgery, then every few weeks to few months. Once your hormones are stable and there are no new problems, you can expect to need tests for your hormones only once or twice a year. Our team would see you earlier if you were feeling unwell at anytime.