Advances in computed tomography (CT) and magnetic resonance imaging (MRI) techniques have improved the visualization of the pituitary region. Increasing numbers of adenomas are diagnosed incidentally during the evaluation of sinus disorders, trauma, and headache. These "incidentalomas" are not necessarily asymptomatic. Although visual deficits are discovered in fewer than 5%, some degree of pituitary dysfunction is found in up to 15% (13). More than one third are macroadenomas and, of these, approximately 25% will show significant enlargement over time (7,13,31,32). Asymptomatic incidental microadenomas are less likely to have clinically significant growth and often can be observed with repeated MRIs.
Most often, pituitary adenomas present secondary to hypersecretion, hypopituitarism, or mass effect (Table 2).
Table 2. Presentation
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Hypersecretion GH secreting adenoma: Acromegaly, ?ACTH secreting adenoma: Cushing's disease ,?Prolactin secreting adenoma: Amenorrhea-galactorrhea, ?TSH secreting adenoma: Secondary hyperthyroidism |
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Pituitary insufficiency ?Symptoms: diminished libido, fatigue, weakness, hypothyroidism ?,Gonadotrophs thyrotrophs somatotrophs corticotrophs |
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Mass Effect Optic chiasm: bitemporal visual field deficit and possibly diminished acuity
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Incidental, Discovered during the evaluation for headaches, trauma, nasal sinus disorders |
(for detailed descriptions see other chapters in Endotext)
Acromegaly presents with characteristic cosmetic changes. There is an insidious coarsening of facial features with an enlarged forehead, enlarged tongue, malocclusion of the teeth, and prognathism. Patients' hands and feet also enlarge. Many patients also report excessive sweating. The external hypertrophy of tissue is paralleled within the body. Patients suffer enlarged organs and overgrowth of joints and cartilage, along with high blood pressure, congestive heart failure, sleep apnea, spinal canal narrowing, and carpal tunnel syndrome. Significant numbers of patients with acromegaly also have impaired glucose metabolism and, often, diabetes mellitus.
Cushing's disease causes changes in body habitus with increased weight, truncal obesity, "buffalo hump", and moon facies. Skin changes are also common and include purple striae, easy bruisability, ruddy complexion, and increased body and facial hair. Patients suffer from fatigue, proximal muscle weakness, osteoporosis, psychological disorders, high blood pressure, and impaired glucose metabolism.
Patients with prolactinomas classically present with amenorrhea or oligomenorrhea and galactorrhea. Most are women in their childbearing years who are more likely to pursue medical attention for infertility and menstrual irregularity. Men, and women beyond their reproductive years, more often have headache, visual symptoms, and signs of decreased pituitary function.
Amenorrhea and galactorrhea are not specific to prolactinomas, however. Prolactin secretion is under constant inhibitory control from the hypothalamus. Any lesion that imposes pressure upon the portal venous connection of the stalk connecting the brain and pituitary gland will interrupt these inhibitory signals, increase serum prolactin, and mimic a prolactinoma, i.e. a 'pseudoprolactinoma'. In such cases serum prolactin levels are usually only moderately elevated. As a general rule, serum prolactin levels over 200 ng/ml (3600mu/l) are associated with prolactinomas.
Tumor growth impairs the normal secretory function of the anterior pituitary and causes hypopituitarism. Common complaints include diminished sex drive, fatigue, weakness, and hypothyroidism. Pituitary insufficiency generally develops slowly over time. Acute pituitary insufficiency occurs in the setting of pituitary apoplexy, a condition in which the tumor infarcts or has internal bleeding. Apoplexy can be particularly devastating because it combines acute hypopituitarism with a rapidly expanding intracranial mass.
Neurologic signs and symptoms develop as adenomas grow beyond the confines of the sella turcica and exert pressure upon adjacent brain structures. As tumors enlarge, they compress the optic nerves and optic chiasm patients experience visual deficits and diminished visual acuity. Classically this causes a bitemporal hemianopsia, visual loss in the temporal fields of each eye. Tumor growth may also affect other nerves (such as the 3rd, 4th, 5th, or 6th cranial nerves) and cause facial pain and/or double vision or drooping of the eyelid. Headache, although a non-specific complaint, can occur when a tumor stretches the dural sac that surrounds the pituitary gland.