A 35-year-old woman is seen in the outpatient clinic for evaluation of an incidental pituitary macroadenoma. Her medical history is significant for hypertension, diabetes, hyperlipidemia, polycystic ovary syndrome, and obesity. She initially presented to the emergency department (ED) a week ago after an episode of right visual field changes that she described as waviness in her right eye and right hemibody sensory changes without motor deficits. While in the ED, she underwent a full workup for possible stroke, which was negative. Magnetic resonance imaging (MRI) of her brain without contrast revealed a 12-mm pituitary lesion; a repeat MRI with contrast was then ordered (Figure). No serum hormonal panel was available for review from ED records.

Upon further questioning of her medical history during the clinic visit, the patient notes that a few years ago she was attempting to become pregnant and was evaluated by her gynecologist for amenorrhea. At that time, she reportedly completed an endocrine laboratory workup that showed a slightly elevated prolactin level between 30 and 40 ng/mL (normal level in nonpregnant women, <30 ng/mL). Per the patient, the minimal elevation was not enough to concern the gynecologist and no MRI was ordered at that time. Her gynecologist recommended that she lose weight. Her menses returned to normal with weight loss. With a history of disrupted menstrual cycles, infertility, and patient reported elevated prolactin level, there is high suspicion for endocrine disruption. A complete pituitary panel is ordered again to examine the current hormone function considering the recent MRI findings. This revealed a prolactin of 33.7 ng/ml, and all other hormonal levels were within normal limits.

Because the patient reports multiple episodes of visual disturbances and the size of the pituitary adenoma on MRI, a neuro-ophthalmology referral is initiated for visual field testing and to determine if the pituitary macroadenoma is causing mass effect and compressing the optic nerve. The neuro-ophthalmologist found she had no visual field defect from her adenoma on visual field testing and believed that her visual disturbances were probably migraine in nature.

Discussion

Pituitary gland tumors are usually found incidentally on imaging studies obtained for other reasons or in workup of patients with abnormal endocrine hormone levels (both decreased and increased levels) or with symptoms of mass effect from the lesions.¹ These tumors are typically benign in nature; cases with malignancy are extremely rare.¹ The exact pathophysiology of pituitary adenomas remains unknown but is thought to be linked to heredity, hormonal influences, and genetic mutations.¹

Pituitary tumors are commonly found in adults between the ages of 35 and 60 years of age.^2,3 The estimated prevalence of pituitary adenomas varies widely by study and findings are typically based on autopsy and radiology data. Surveillance, Epidemiology, and End Results (SEER) Program data from 2004 to 2018 show an incidence rate of pituitary adenomas and pituitary incidentalomas of 4.28 ± 0.04 and 1.53 ± 0.02 per 100,000 population.⁴ Pituitary tumors have been found in 14.4% of unselected autopsy cases and 22.5% of radiology tests.¹

The SEER data suggest that incidence rates are similar among women and men but are higher among women in early life and higher among males in later life.⁵ Rates of prolactinomas (prolactin-secreting tumors) and corticotropinomas (adrenocorticotropic hormone-secreting tumors; Cushing disease) are higher in women than men.⁶

Earlier SEER data showed a significantly higher incidence of pituitary adenomas in Black individuals compared with other racial/ethnic groups; several factors may account for this discrepancy such as the higher stroke rate in this population, which leads to a greater likelihood for brain imaging that detects incident pituitary tumors.⁵

Incidental findings of pituitary adenoma may be found during workup related to hormonal dysfunction (amenorrhea, galactorrhea, fertility disorders, sexual dysfunction), noticeable vision change, new-onset headaches, or imaging performed for other diagnostic purposes.⁷

 

Pituitary Types

Pituitary tumor types are differentiated by location, size, and functional status. Pituitary tumors commonly arise from the anterior portion of the gland (adenohypophysis) and rarely from the posterior portion (neurohypophysis).² Both adenohypophyseal and neurohypophyseal tumors are commonly benign and slow-growing.¹ Malignant pituitary tumors account for less than 1% of pituitary lesions and are usually metastases from breast and lung cancers.³ Adenohypophyseal carcinoma is rare, with less than 140 reported cases.²

Pituitary tumors are categorized by the size^1,2:

• Microadenomas (<10 mm)
• Macroadenomas (>10 mm to 40 mm)
• Giant adenomas (>40 mm)

Pituitary adenomas are further classified as functioning (hormone-secreting) or nonfunctioning (nonsecreting).^1,6 If the adenoma is functioning, hormone levels will be found in excess. If the levels are within normal limits, a nonfunctioning pituitary adenoma is suspected.

Functioning Tumors

Approximately 65% of all pituitary adenomas are functioning tumors.² Functioning pituitary adenomas present in various ways depending on which hormone is involved and the level of hormone secretion. Prolactinomas are the most common type of functioning adenomas followed by growth hormone-secreting and adrenocorticotropic hormone-secreting pituitary tumors. Adenomas secreting thyrotropin and follicle-stimulating hormone are less commonly found.² Clinical features of functional pituitary adenomas are outlined in Table 1.^2.8

Table 1. Clinical Features and Laboratory Findings of Functioning Pituitary Adenomas

Nonfunctioning Tumors

Approximately 20% to 30% of pituitary adenomas are nonfunctional.³ These tumors may go undiagnosed for years until the mass of the tumor starts to effect surrounding structures and causing secondary symptoms such as compression of the optic chiasm causing vision impairments.

Nonfunctioning pituitary adenomas and prolactinomas (functioning) are the 2 most common types of pituitary adenomas.^2,3 The consulting clinician must understand the difference in pathology of these 2 types of lesions, what diagnostic test to order, how to interpret the test results, and which specialty to refer the patient to best on the initial workup findings.

Initial Workup

Proper baseline workup should be initiated before referring patients with incidental pituitary adenoma 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.

Imaging

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 a pituitary adenoma is an incidental finding on another 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

Perimetry

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 adenoma 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.

Conclusion

A thorough workup including laboratory testing, imaging, and vision field testing is the foundation of an effective referral process for 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.

References

1. Russ S, Anastasopoulou C, Shafiq I. Pituitary adenoma. 2021 Jul 18. In: StatPearls. StatPearls Publishing; 2022 Jan–. Updated July 18, 2021.

2. Greenberg MS. Tumors of non-neural origin. In: Handbook of Neurosurgery, 9th ed. Thieme Medical Publishers: 2019; 1655-1755

3. Yeung M, Tahir F. The pathology of the pituitary, parathyroids, thyroid and adrenal glands. Surgery. 2020;38(12):747-757.

4. Watanabe G, Choi SY, Adamson DC. Pituitary incidentalomas in the United States: a national database estimate. World Neurosurg. 2021:S1878-8750(21)01780-0. doi:10.1016/j.wneu.2021.11.079

5. McDowell BD, Wallace RB, Carnahan RM, Chrischilles EA, Lynch CF, Schlechte JA. Demographic differences in incidence for pituitary adenoma. Pituitary. 2011;14(1):23-30. doi:10.1007/s11102-010-0253-4

6. Molitch ME. Diagnosis and treatment of pituitary adenomas: a review. JAMA. 2017;317(5):516-524. doi:10.1001/jama.2016.19699

7. Yao S, Lin P, Vera M, et al. Hormone levels are related to functional compensation in prolactinomas: a resting-state fMRI study. J Neurol Sci. 2020;411:116720. doi:10.1016/j.jns.2020.116720

8. Beck-Peccoz P, Persani L, Lania A. Thyrotropin-secreting pituitary adenoma. In: Feingold KR, Anawalt B, Boyce A, et al, ed. Endotext. MDText.com, Inc.; 2019.

9. Yadav P, Singhal S, Chauhan S, Harit S. MRI evaluation of size and shape of normal pituitary gland: age and sex related changes. J Clin Diagnostic Research. 2017;11(12):1-4. doi:10.7860/JCDR/2017/31034.10933

10. Varrassi M, Cobianchi Bellisari F, Bruno F, et al. High-resolution magnetic resonance imaging at 3T of pituitary gland: advantages and pitfalls. Gland Surg. 2019;8(Suppl 3):S208-S215. doi:10.21037/gs.2019.06.08

11. Shimon I. Giant prolactinomas. Neuroendocrinology. 2019;109(1):51-56. doi:10.1159/000495184

12. Vié AL, Raverot G. Modern neuro-ophthalmological evaluation of patients with pituitary disorders. Best Pract Res Clin Endocrinol Metab. 2019;33(2):101279. doi:10.1016/j.beem.2019.05.003

From the March/April 2022 Issue of Clinical Advisor