Pituitary Tumors | Dr. Prem Pillay, Singapore
Pituitary tumors that occur from the pituitary gland which can be described as the “Master” hormone gland of the body which is located below the base of the brain and in front of the brainstem . It sits in a bony fossa (depression) called the sellar turcica. It is divided into an anterior lobe and a posterior lobe (with a small intermediate lobe).
Pituitary tumors account for about 15% of all intracranial tumors.
Mean age: 20 to 50 years
Sex: More females and males for prolactin and ACTH secreting tumors and a male predominance for GH-producing tumors.
Microadenomas are tumors less than 10mm in size and Macroadenomas are more than 10mm in size. Local invasion can occur with macroadnenomas particularly into the skull base regions such as the cavernous sinus. Superior growth of macroadenomas can compress the optic chiasm/optic nerves and cause visual disturbances. Malignancy is rare (<1% of all pituitary tumors).
Prolactin producing tumors are the most frequent type of pituitary tumor (30%). Failure of menstruation (amenorrhea) and milk production from the breasts in non-pregnant females (galactorrhea) are the common symptoms. In men decreased libido and impotence and visual loss are commoner symptoms as the tumors tend to be larger when discovered.
Growth hormone secreting tumors are the second commonest hormone producing pituitary tumors (15%).
It can cause children to grow into “giants” (gigantism) and break height records in their communities. In adults it can cause acromegaly with an enlarged head, hands and feet.
ACTH producing tumors (10%) can cause Cushing’s disease. Such patients have central obesity, a moonface, and abdominal marks called striae.
TSH secreting tumors are rare (1%) and and cause symptoms of hyperthyroidism. Null cell tumors are the second most common tumor and do not produce hormones (25%). They can grow to a large size and cause visual loss before detection. They can be invasive.
Diagnosis of pituitary tumors: This is based on the clinical symptoms and signs mentioned above. An emergency situation can be created by sudden bleeding in a tumor called pituitary apoplexy. This can cause sudden loss of vision and even collapse and coma.
Blood tests of all the common pituitary hormones is carried out.
Vision tests such as Visual Fields and retinal photographs can reveal visual loss and its extent.
MRI with contrast (gadolinium) is superior to CT scanning in diagnosis particularly for the smaller microadenoams. Some patients with ACTH producing microadenomas are difficult to find and selective venous sampling of the hormone may be required by angiography.
Diffrential Diagnosis: Nelson’s syndrome is an enlargement of the pituitary gland caused by a surgical adrenalectomy. Lymphocytic hypophysitis can cause a tumor like appearance but it is an autoimmune disease. Giant cell pituitary granulomas and Tuberculous granulomas can be mistaken for pituitary tumors on MRI or CT.
Hormone secreting tumors which are microadenomas can be treated by oral medications like bromocriptine (parlodel). GH secreting tumors can be treated with oral medication like octreotide.
For tumors that do not respond to medical treatment or if patients have side effects from medical treatment then alternatives are surgery or radiosurgery.
Surgery: In the past this was carried out using an open craniotomy and then later with open approaches through the nose or above the teeth through the mouth.
Modern approaches include Endoscopic approaches through the nasal passages with microsurgical methods.
Computer guidance (StealthStation) can be used to guide such minimally invasive microsurgery.
Radiosurgery: Gamma knife and stereotactic radiotherapy (SRT) are more focused treatments than traditional radiotherapy. There is a more precise treatment of tumors with less side effects. The latest technologies include Tomotherapy (NeuroTomotherapy).
Combined Endosocpy/ Microsurgery and Radiosurgery: In patients with large invasive tumors, combination treatment may be safer and effective than single modality treatments.
Ultimately the best treatment methods and choices are determined by an experienced Neurosurgeon based on all the available information and presented to the patient for his or her final decision.