Signs and Symptoms
Prolactinomas, the most common form of pituitary tumor, cause amenorrhea (the loss of menstruation), galactorrhea (the spontaneous flow of milk from the breast), and infertility in females. They cause hypogonadism, decreased libido and impotence in males. Tumors that secrete excess growth hormone cause gigantism in children and acromegaly in adults. Adrenocorticotropic hormone (ACTH) secreting adenomas produce Cushings disease (hyperadrenalism). Symptomatic pituitary adenomas comprise 12 to 15 percent of all intracranial tumors, and must be differentiated from non-neoplastic mass lesions.
Visual symptoms vary and include bitemporal visual field loss more dense from the superior to inferior, color desaturation, diplopia as well as ophthalmoplegia tumors expand into the cavernous sinus. The funduscopic sign of long-standing chiasmal compression is primary optic atrophy (secondary to retrograde axonal degeneration). Severe optic atrophy indicates a poor prognosis for visual recovery following surgical decompression. (For visual field printout, see "Understanding Visual Fields and the Visual Pathways" page 56.)
Pituitary adenomas typically are slow growing, benign neoplasms of epithelial origin. In most circumstances they arise from the adenohypophysis (the anterior lobe of the pituitary gland) and are capable of producing both systemic and visual signs. Approximately 8 mm to 13 mm above the pituitary gland is the optic chiasm. The nasal retinal fibers of each eye (temporal visual field) cross at this point, proceeding into the contralateral optic tract.
Upwardly growing pituitary tumors, which reach appropriate sizes, impinge on the anterior notch of the chiasm at its lowest lying aspect. This produces the bitemporal hemianopsia with increased density superiorly. Since tumor growth is usually asymmetrical, the field loss between two eyes is also typically asymmetrical.
Diseases affecting the pituitary gland produce two types of disturbances: mechanical and hormonal. Mechanical disturbances occur whenever a tumor compresses adjacent structures. Hormonal manifestations result when hyper-or hyposecretions occur. Pituitary adenomas are further differentiated by size. Microadenomas have little impact on the visual system or gland function and are defined as intrasellar adenomas that measure up to one centimeter in diameter without sellar enlargement. Macroadenomas present with mass effect symptoms such as headaches and measure larger than one centimeter with generalized sellar enlargement. Macroadenomas include (in order of most common to least common): non-secreting adenomas, prolactin secreting (chromaphobe) adenomas, growth hormone secreting (acidophil) adenomas, ACTH secreting (basophil) adenomas and FSH or TSH secreting adenomas.
Secreting tumors are usually diagnosed by general physicians and endocrinologists. Non-secreting tumors are often diagnosed by eye care practitioners because they produce visual symptoms in the absence of systemic signs.
In pregnant women, bitemporal visual field loss and headache may signal pituitary apoplexy (rapid degeneration with hemorrhagic necrosis of the pituitary gland). Pituitary apoplexy is a potentially life-threatening condition. Any woman with sudden onset of headache and suspicious visual symptoms (confirmed by perimetry) should be referred for a MRI with or without lumbar puncture to rule out subarachnoid hemorrhage from the this type of tumor. Women with pituitary adenomas and MRI evidence of subarachnoid bleeding should deliver by cesarean section to avoid risk of apoplexy during delivery. Postpartum hemorrhage can cause infarction of the pituitary gland leading to hypopituitarism (Sheehans syndrome).
Other reports in this section
Eyelids & Eyelashes | Conjunctiva & Sclera | Cornea
Uvea | Vitreous & Retina | Optic Nerve & Brain | Oculosystemic Disease
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