What labs are used to assess pituitary adenoma in males?

Laboratory Assessment of Pituitary Adenoma in Males

The essential laboratory workup for pituitary adenoma in males should include serum luteinizing hormone (LH), prolactin, and additional hormone testing based on clinical presentation, followed by MRI of the sella with contrast for definitive diagnosis. 1

Initial Hormone Assessment

Core Laboratory Tests:

• Luteinizing Hormone (LH): Critical to establish etiology of testosterone deficiency and determine if it's primary or secondary 1
• Prolactin: Essential in all patients with suspected pituitary adenoma, particularly with low testosterone and low/normal LH 1
• Total Testosterone: Baseline measurement to assess hypogonadism 1

Additional First-Line Hormone Tests:

• Follicle-Stimulating Hormone (FSH): Important for reproductive assessment and to identify gonadotroph adenomas 1, 2
• Thyroid Function Tests: TSH, free T4, free T3 (to identify TSH-secreting adenomas) 1, 3
• Morning Cortisol/ACTH: To screen for corticotroph adenomas 4
• IGF-1: To screen for growth hormone-secreting adenomas 4, 5
• Estradiol: Particularly in males with breast symptoms or gynecomastia 1

Specialized Testing Based on Initial Results

For Low Testosterone with Low/Normal LH:

• Repeat Prolactin Measurement: To confirm persistent elevation and rule out spurious results 1
• MRI of Sella: Required for all patients with persistently elevated prolactin 1

For Suspected Cushing's Disease:

• Late-Night Salivary Cortisol: Best screening test for hypercortisolism 4
• Dexamethasone Suppression Test: To confirm ACTH-dependent Cushing's syndrome 1

For Suspected Growth Hormone Excess:

• Glucose Tolerance Test: To assess GH suppression in patients with elevated IGF-1 5

Imaging Studies

• MRI of the Sella with Contrast: Gold standard for visualizing pituitary adenomas 1

  • High-resolution pituitary protocols
  • Dynamic contrast-enhanced imaging for microadenoma detection
  • Thin-section imaging (especially for tumors <10mm)

• CT Sella: Alternative when MRI is contraindicated, though less sensitive 1

Special Considerations

For Patients with Negative MRI but Strong Clinical Suspicion:

• Inferior Petrosal Sinus Sampling: For ACTH-dependent Cushing's syndrome with equivocal imaging 1

For Post-Surgical Evaluation:

• Repeat Hormone Testing: 4-6 weeks post-surgery to assess cure 6

Important Caveats

• Ki-67 index ≥3% combined with local invasion on imaging predicts a 25% recurrence rate after surgery 1
• Men with total testosterone levels <150 ng/dL and low/normal LH should undergo pituitary MRI regardless of prolactin levels 1
• Screening questionnaires are not appropriate substitutes for laboratory testing 1
• Genetic testing should be considered in all patients with pituitary adenomas, especially those with GH and prolactin excess 1

Algorithmic Approach

1. Initial assessment: Measure total testosterone, LH, FSH, prolactin, TSH, free T4, free T3, IGF-1, and morning cortisol/ACTH
2. If prolactin is elevated: Repeat measurement to confirm
3. If testosterone is low with low/normal LH: Order MRI of sella with contrast
4. If IGF-1 is elevated: Perform glucose tolerance test for GH suppression
5. If morning cortisol/ACTH suggests hypercortisolism: Perform late-night salivary cortisol and dexamethasone suppression test
6. For all confirmed pituitary adenomas: Proceed to MRI for tumor characterization

This comprehensive laboratory assessment allows for proper identification of the adenoma type and guides appropriate treatment decisions to reduce morbidity and mortality associated with pituitary adenomas.