Back to Site
Pituitary Adenomas are the most common cause of sellar masses since third decade. They account for 10-25% of all intracranial neoplasms. Most adenomas are benign and slow-growing tumors of the anterior pituitary gland. The pituitary carcinomas are extremely rare. Metastasis to pituitary gland is uncommon and seen in elderly with lung and breast cancers being the most common primary sites. Most pituitary adenomas occur spontaneously. However, there are cases of familial pituitarytumours. Multiple endocrine neoplasia: Type 1 (MEN 1) is a rare condition characterised by simultaneous tumors of pituitary, pancreas and parathyroid gland.
Classification
Adenomas are classified on basis oftheir size and origin of the cell. Lesions that are smaller than 1cm are called microadenomas and lesions larger than 1cm are called macroadenomas. Adenomas can arise from any type of cell of the anterior pituitary gland and can result in increased secretion of the hormone produced by that cell. These are called functional tumors whereas; tumors that do not release any active hormone are called non-functioning adenomas.
Clinical manifestations
Pituitary adenomas can present with neurologic symptoms, symptoms related to over or under secretion of pituitary hormones or as an incidental finding on radiologic examination done for some other reason (incidentalomas).
Visual defects
Visual impairment is one of the most common symptoms within a non-functioning adenoma. It occurs when macroadenomas grow upward in the brain cavity, compressing the optic chiasm. The most common complaint is loss of vision in the temporal fields called as bitemporal hemianopia. Decreased visual acuity i.e. blurred vision occurs if the macroadenoma grows forward and compresses on optic nerve. As the onset of visual deficit is gradual, many patients do not see an ophthalmologist for months or years. Other neurological manifestations of pituitary adenomas include headache (which is non specific) and diplopia (caused by lateral extension of the tumor causing oculomotor nerve compression).
Clinical effects of hypersecretion of hormones by pituitary adenoma
Prolactin producing pituitary adenoma (Prolactinoma) – Hyperprolactinaemia causes irregular periods and galactorrhoea in women and hypogonadism in men. Llke men, postmenopausal women often do not have the typical symptoms but usually show symptoms of mass effect such as headaches and visual disturbances. ACTH secreting pituitary adenoma – Cushing’ s disease results when pituitary adenoma secretes excess amount of ACTH. Its symptoms include weight gain, truncal obesity, easy bruising of skin, hypertension and muscle weakness. Growth hormone secreting pituitary adenoma – Excess
production of growth hormone causes acromegaly m adults and gigantism in children. TSH – secreting pituitary adenoma – Excess TSH hormone production leads to hyperthyroidism. Tumours like these are rarely found.
Clinical effects of pituitary hormonal deficiency
Large pituitary tumors can compress the normal pituitary gland causing hypopituitarism. The symptoms of hypopituitarism depend upon the affected hormone. Reduction in luteinizing hormone (LH) and follicle stimulating hormone (FSH) can cause hypogonadism leading to reduced libido and erectile dysfunction in men and infertility in women. Reduction in TSH production can lead to secondary hypothyroidism which can cause weight gain, fatigue and decreased mental function. When ACTH secretion is reduced, adrenal insufficiency occurs. Typical symptoms of adrenal sufficiency include fatigability, hypotension and electrolyte imbalances. When growth hormone secretion is affected, it causes stunted growth and delayed puberty in children and generalised tiredness and loss of muscle mass and tone in adults.
Pituitary apoplexy
Pituitary adenomas can cause sudden internal bleeding leading to abrupt increase in size. Patients with pituitary apoplexy generally experience sudden headaches associated with acute vision loss and hypopituitarism. All pituitary hormonal deficiencies can occur but cortisol deficiency is the most serious as it can cause severe hy potension. Surgical decompression is performed in cases with severe visual impairment or neurological symptoms.
Diagnosis
A pituitary adenoma maybe suspected based on symptoms and physical findings. Standard diagnostic tests include hormone testing and imaging scans. Pituitary hormone testing is necessary for every patient with suspected pituitary tumour. This can help to detect any functional adenoma as well as determine any evidence of hypopituitarism. MRI is the most commonly used imaging modality for detecting pituitary adenomas. Sometimes CT scan is also used for the same.
Treatment
Management of a pituitary adenoma depends upon the type of tumour and the size of the tumour. Treatment modalities include medical therapy, transphenoidal surgery & radiotherapy. Dopamine agonists such as bromocriptine or cabergoline are the first-line treatment in patients with prolactinomas. They effectively normalise prolactin levels and reduce the tumour volume. Growth hormone secreting tumors are initially treated with surgery but medical treatment with somatostatin analogues and cabergoline is often required. Similarly, the primary treatment of Cushings disease is surgical resection of the adenoma but medical therapies with ketoconazole, somatostatin analogues and mifepristone maybe given for those not cured by surgery. Surgery is generally required for nonfunctioning adenomas. Radiation is reserved for tumors that cannot be removed surgically or for patients who do not respond to medical therapy.
A surgical plan is indicated when the patient has visual problems due to compression of optic nerves by the tumour, hormonal deficiency or excess not responding to medical therapy or pressure effects in brain due to large size of the tumour.
Most operations on the pituitary gland are now carried out through the nose traditionally performed using fibre optic endoscopes. This is called trans-nasal trans-sphenoidal endoscopic pituitary surgery. This procedure is minimally invasive, relatively pain-free and leaves no scar while simultaneously allowing safe and complete removal of tumour under vision. Another approach through the skull (transcranial pituitary surgery) is reserved for large and complex pituitary tumours which are a rare occurrence. The residual or recurrent tumour can be treated by radiosurgery/gamma knife surgery. Surgery to remove a pituitary tumour carries certain risks that one should be aware of· although low probability, these risks includ infection, bleeding, and CSF ( cerebra-spinal fluid) leak.
At Kokilaben Dhirubhai Ambani Hospital we have successfully accomplished over 300 pituitary tumour excisions in last 8 years. The use of state-of-the-art endoscopic system with resection accuracy enhanced by use of navigation system and intra-operative MRI gives superior results.