The pituitary gland is responsible for releasing many of the body's vital hormones into the blood. These hormones include growth hormone, prolactin, thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), luteinising hormone and vasopressin. They are involved in numerous physiological processes and systems, including reproduction, growth, blood pressure control and inflammation.
A tumour of the pituitary gland is a growth which can either lead to excessive release of one or more of these hormones, or it can restrict the release of hormones. Most commonly, growth hormone or prolactin are the hormones affected by a tumour.
Pituitary tumours are almost always benign, and therefore do not spread to other areas. However, their growth which affects the hormonal system, and their close proximity to the brain, are cause for concern and require treatment.
Depending on whether the tumour is benign or malignant, they are referred to as adenomas or carcinomas, respectively.
An entirely separate classification exists, depending on the hormones that are affected by the tumour. For example, the most common hormone affected is prolactin, and the tumour is called a prolactinoma.
If the tumour restricts the release of hormones, it is termed hypopituitarism.
As with many forms of cancer, the exact cause of pituitary tumours is unknown, though they are caused by the uncontrolled cell growth and division, stimulated by the DNA.
Because the tumour can affect different hormones, the signs and symptoms differ widely. Each is discussed briefly below:
- Tumours affecting prolactin
This is the most commonly affected hormone. If excessive prolactin is released, the result may be a decrease in the normal levels of sex hormones. In women, the symptoms this causes include irregular or completely absent menstrual periods, and excessive milky discharge from the breasts. In men, symptoms may include enlarged breasts (called gynaecomastia), erectile dysfunction, impotence, infertility and decreased body hair.
- Tumours affecting growth hormone
Excessive growth hormone can cause a condition known as acromegaly, the symptoms of which include enlarged hands, feet and jaw-bone, high blood pressure and heart problems. In children, accelerated growth results in a condition described as gigantism.
ACTH is a hormone which stimulates the kidneys to release cortisol. If excessive cortisol is released, a condition called Cushing's Syndrome develops. Symptoms include weight gain in the waist, stomach and upper back, exaggerated facial roundness (termed "moon-face"), a characteristic hump on the upper part of the back, increased blood pressure, muscle weakness and thinning of the skin.
- Tumours affecting thyroid-stimulating hormone (TSH)
When the tumour affects TSH release, excessive amounts of thyroxine are ultimately released into the blood. While rare, the symptoms include sudden weight loss, rapid and irregular heartbeats, nervousness and irritability.
In addition to these specific symptoms, general symptoms include headaches, partial loss of vision as a result of the compression of the optic nerve, nausea, constipation, weakness, fatigue, and sudden changes in weight.
Blood tests are performed to detect potentially abnormal levels of hormones in the blood. Further testing includes imaging of the brain, either with CT scans or MRI scans.
Treatment varies depending on the location, size, severity and influence of the tumour. The most common treatment is surgery during which the affected area is removed. Alternatively, if surgery is not an option, radiation therapy can be used.
Medical treatments can be used to slow down tumour growth, and to block the release of the affected hormones.
Finally, in some cases, the tumour produces no clinical symptoms, and so surgical or medical intervention is not required. In this case, regular check-ups and observation can be used to track possible changes.
The prognosis is again very dependent on the tumour and its specific location, size and influence. As mentioned, there are occasions where the tumour has little to no effect on the normal function of the patient. In cases where surgery is required, the prognosis if influenced by the location and size of the tumour, though in many cases the prognosis is good. Often, because sections of the gland are removed, the patient will have to supplement with replacement hormones.
When to call your doctor
If any of the above specific symptoms are experienced, a consultation is advised. Serious symptoms such as those described for the specific hormones, as well as blurred vision, persistent headaches and sudden weight changes warrant a medical opinion.
Reviewed by Dr David Eedes, Oncologist, March 2011