What is the initial work‑up for a suspected pituitary adenoma?

Initial Work-Up for Suspected Pituitary Adenoma

Order high-resolution MRI of the sella with and without IV contrast as the gold standard imaging study, combined with comprehensive anterior pituitary hormone testing including prolactin, IGF-1, thyroid function (TSH, free T4), morning cortisol with ACTH, and gonadal hormones to assess for both hypersecretion and hypopituitarism. 1, 2

Imaging Evaluation

First-Line Imaging

• MRI using high-resolution pituitary protocols is the preferred diagnostic modality for evaluating suspected pituitary adenomas, as it directly visualizes the pituitary gland, infundibulum, optic chiasm, and vascular structures with superior sensitivity compared to all other modalities 1
• Thin-section T1-weighted coronal and sagittal sequences before and after IV gadolinium administration maximize detection of microadenomas (<10 mm), which appear as hypoenhancing lesions 1, 3
• Dynamic contrast-enhanced imaging increases sensitivity for detecting small adenomas and their relationship to the pituitary stalk and cavernous sinus 1, 3
• Spoiled gradient-echo 3-D T1 sequences show increased sensitivity for hormone-secreting adenomas 1

Alternative Imaging (Not Recommended as Initial Study)

• CT with contrast can identify large pituitary tumors and may define some microadenomas, but MRI is significantly more sensitive and CT should not be used as the initial imaging study 1
• Plain radiography of the sella is insensitive and nonspecific, as pituitary adenomas frequently occur with normal sella size 1

Comprehensive Hormonal Assessment

Mandatory Screening for All Patients

• Prolactin level is mandatory in all patients, as prolactinomas account for 32-66% of pituitary adenomas and are the most common functioning tumor type 2, 4
• IGF-1 testing is essential to detect clinically silent growth hormone-secreting tumors, as up to 46% of apparently nonfunctioning adenomas show GH immunostaining despite lack of clinical acromegaly 2
• Thyroid axis testing (TSH and free T4) is necessary to detect central hypothyroidism, which occurs in 8-81% of patients with pituitary adenomas 2
• Adrenal axis testing (morning cortisol and ACTH) is necessary to detect adrenal insufficiency, which occurs in 17-62% of patients 2
• Gonadal axis testing (testosterone in men, estradiol and LH/FSH in premenopausal women) is necessary as hypogonadism is one of the most commonly affected axes 2

Clinical Context for Hormone Testing

• The prevalence of hypopituitarism in pituitary adenomas is substantial and often exceeds clinical suspicion, making comprehensive testing essential even in asymptomatic patients 2
• Hormone-secreting adenomas are most commonly microadenomas (<10 mm) at presentation, particularly in premenopausal females who present with amenorrhea and galactorrhea 1
• In males, prolactinomas may be asymptomatic until visual symptoms occur from optic chiasm compression or present with hypogonadotropic hypogonadism causing loss of libido and impotence 1

Additional Essential Testing

Visual Assessment

• Formal visual field testing by an ophthalmologist is required for any tumor abutting or compressing the optic chiasm or nerves 4, 5
• Visual field defects occur in 18-78% of patients with macroadenomas (≥10 mm) 4

Baseline Laboratory Studies

• Electrolytes and renal function testing are essential for perioperative management and to assess for diabetes insipidus, which occurs in approximately 7% of cases 2
• Exclude secondary causes of hyperprolactinemia before attributing elevated prolactin to an adenoma: pregnancy, primary hypothyroidism, renal insufficiency, and medications (antipsychotics, antiemetics, antidepressants) 3

Genetic Testing (Selected Cases)

• Routine genetic testing is not recommended unless a familial syndrome is suspected, particularly in children and adolescents where certain genetic conditions are associated with pituitary adenomas 2, 6

Critical Pre-Treatment Considerations

Mandatory Hormone Replacement

• Preoperative hormone replacement is mandatory for patients with adrenal insufficiency and significant hypothyroidism before any surgical intervention, as failure to do so can result in life-threatening adrenal crisis 2
• Comprehensive testing determines the need for replacement therapy, as cutoff values for initiating replacement differ in panhypopituitarism versus isolated deficiencies 2

Coordination of Care

• Coordination with endocrinology is necessary for interpretation of pituitary hormone testing, particularly for dynamic testing that may be needed in selected cases 2
• Dynamic stimulation and suppression tests are performed in selected situations for detecting specific types of hypersecretion or response to treatment 7

Common Pitfalls to Avoid

• Do not use CT as the initial imaging study, as it is particularly insensitive for microadenomas <5 mm compared to MRI 3
• Do not skip prolactin testing even if clinical suspicion is low, as prolactinomas are the most common functioning adenoma and may be clinically silent 2, 4
• Do not delay visual field testing if the tumor abuts the optic apparatus, as visual deficits are a strong indication for urgent surgical intervention 5
• Do not proceed to surgery without ensuring adequate adrenal and thyroid replacement in deficient patients, as this creates significant perioperative risk 2