Proper baseline workup should be initiated before referring patients with incidental pituitary adenomas to a specialist. The initial workup includes imaging, blood work to determine if the pituitary adenoma is causing hormonal dysfunction, and neuro-ophthalmology referral for visual field testing to determine if the optic nerve/chiasm is impacted.
The most accurate diagnostic modality of pituitary gland pathology is MRI with and without contrast. The MRI should focus on the hypothalamic-pituitary area and include contrasted imaging to evaluate the soft tissue within the intracranial structure.9 The coronal and sagittal views are the best to display the pituitary gland width and height and identify abnormalities.9 The MRI provides a detailed evaluation of the pituitary gland related to adjacent structures within the skull, which helps to detect microalterations of the pituitary gland.10 If incidental pituitary adenomas are found on an imaging modality (such as a computed tomography scan or MRI without contrast), an MRI with and without contrast that focuses on the pituitary gland should be obtained.
Pituitary Laboratory Panel
A complete pituitary panel workup should be obtained including prolactin, thyrotropin, free thyroxine, cortisol (fasting), adrenocorticotropic hormone, insulinlike growth factor 1, growth hormone, follicle-stimulating hormone, luteinizing hormone, estradiol in women, and total testosterone in males.1 Tests should be completed in the morning while fasting for the most accurate results. For instance, normally cortisol levels drop during fasting unless there is abnormality. Table 2 below shows normal laboratory ranges for a complete pituitary panel.
Serum prolactin levels can slightly increase in response to changes in sleep, meals, and exercise; emotional distress; psychiatric medications; and oral estrogens. If the initial prolactin level is borderline high (21-40 ng/mL), the test should be repeated. Normal levels are higher in women than in men. Microadenomas may cause slight elevations in prolactin level (ie, <200 ng/mL), while macroadenomas are likely to cause greater elevations (ie, >200 ng/mL).1 Patients with giant prolactinomas typically present with prolactin levels ranging from 1000 ng/mL to 100,000 ng/mL.11
Pituitary adenomas may cause ophthalmologic manifestations ranging from impaired visual field to diplopia because of upward displacement of the optic chiasm. The optic chiasm is located above the pituitary gland and a pituitary tumor that grows superiorly can cause compression in this area.12 Optic chiasm compression from a pituitary adenoma commonly causes bitemporal hemianopsia.2 If the tumor volume is promptly reduced by surgical resection or medication (in the case of prolactinomas), initial vision changes due to compression may be reversible.12
Baseline and routine follow-up perimetry are important in patients with pituitary adenoma, as symptoms of optic chiasm compression may go unnoticed by patients as visual field deficits often develop gradually. Also, post-treatment perimetry assessments can be used to compare the initial testing to evaluate reversible visual field deficits. It is recommended that patients with pituitary adenomas (both function and nonfunctiong) receive neuro-ophthalmologic evaluations twice a year to ensure no visual changes have occurred.12
Referral to a Specialist
Management of pituitary adenomas requires a multidisciplinary team of specialists including endocrinologists, neurosurgeons, and neuro-ophthalmologists. The type of adenoma governs which specialist patients with incidental pituitary adenomas should see first.
Patients with functioning pituitary adenomas should be referred to an endocrinologist before a neurosurgeon. The most prevalent functioning adenomas, prolactinoma, are initially treated with dopamine agonist medications.1,6 A patient with prolactinoma would only need to see a neurosurgeon if they have a macroadenoma that is not responsive or only partially responsive to dopamine agonists therapy or is causing vision deficits related to compression of the optic chiasm.2
Patients with nonfunctioning pituitary adenomas should first be referred to a neurosurgeon to discuss surgical options versus observation. The recommended treatment for patients with nonfunctioning adenomas and clinical features of mass effect (ie, visual deficits) is surgery.1,6 If the patient is asymptomatic with no signs of visual field deficits, the neurosurgery team may recommend continued surveillance with serial imaging and serial perimetry screenings.12
The patient in the case was found to have a nonfunctioning pituitary adenoma (prolactin was 33.7 ng/mL). Neuro-ophthalmology did not find any visual field defect upon initial assessment; the patient decided to continue observation with serial imaging (MRI) and serial neuro-ophthalmology assessments. Serial imaging with MRI brain revealed slow but real progression of the pituitary macroadenoma (12 mm initially; 13 mm 6 months later; and 14 mm 1 year from initial MRI findings). Although the patient still did not have any visual field defects per the neuro-ophthalmology reassessments, the documented growth on MRI over a short period of time was enough to make the patient more amendable to surgical resection. The patient underwent trans-sphenoidal resection of the pituitary lesion approximately 16 months after discovery of the tumor.
A thorough workup including laboratory testing, imaging, and vision field testing is the foundation of an effective referral process for incidental pituitary adenomas and guides which specialist is consulted first. If patients are referred before initial workup is completed, delays in care, unnecessary specialty visits, and increased overall health care costs may occur.
Melissa Wasilenko, MSN, RN, is a registered nurse at Lyerly Neurosurgery in Jacksonville, Florida. She is currently pursuing a doctorate in nursing practice with a focus in family medicine at the University of North Florida in Jacksonville.
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