From the Guidelines
Evaluation of a pituitary mass requires a comprehensive approach, starting with a complete pituitary hormone panel, including prolactin, growth hormone with IGF-1, ACTH with cortisol levels, TSH with free T4, LH, FSH, and testosterone in men or estradiol in women, as recommended by recent guidelines 1. When evaluating a pituitary mass, it is essential to consider the potential for the "high-dose hook effect" in prolactin measurement, which can lead to artificially low results in cases of very high prolactin concentrations 1.
Initial Laboratory Testing
- Prolactin levels should be measured first, as hyperprolactinemia may indicate a prolactinoma or stalk effect
- Growth hormone with IGF-1 to assess for acromegaly
- ACTH with cortisol levels (morning and after dexamethasone suppression test) to evaluate for Cushing's disease
- TSH with free T4 to assess thyroid function
- LH, FSH, and testosterone in men or estradiol in women to evaluate gonadal function
Dynamic Testing
- Growth hormone suppression test with oral glucose
- ACTH stimulation test with cosyntropin
- CRH stimulation test
Imaging Studies
- Contrast-enhanced MRI of the pituitary is the gold standard, providing detailed visualization of the mass and its relationship to surrounding structures 1
- Visual field testing is essential when the mass approaches the optic chiasm to assess for visual deficits
Additional Testing
- Bone mineral density scans if hypercortisolism or hypogonadism is suspected
- Basic metabolic panels to evaluate for diabetes insipidus or electrolyte abnormalities It is crucial to note that the evaluation of a pituitary mass should be individualized, and the choice of tests may vary depending on the patient's symptoms and clinical presentation, as well as the results of initial laboratory and imaging studies 1.
From the Research
Basic Labs for Evaluating a Pituitary Mass
To evaluate a pituitary mass, several basic labs are recommended:
- Prolactin levels: Hyperprolactinemia is a common finding in patients with pituitary adenomas, particularly prolactinomas 2, 3
- Adrenocorticotropic hormone (ACTH) and cortisol levels: These tests can help diagnose Cushing's disease, which can be caused by a pituitary adenoma 4, 5, 6
- Growth hormone and insulin-like growth factor 1 (IGF-1) levels: These tests can help diagnose acromegaly, which can be caused by a pituitary adenoma 4, 5
- Thyroid function tests: These tests can help evaluate the function of the thyroid gland, which can be affected by a pituitary mass
- Electrolyte panel: This test can help evaluate the patient's electrolyte balance, which can be affected by a pituitary mass
Additional Tests
Additional tests may be ordered based on the patient's symptoms and the results of the basic labs:
- Dexamethasone suppression test: This test can help diagnose Cushing's disease 4, 5
- Midnight salivary cortisol test: This test can help diagnose Cushing's disease 4
- Oral glucose tolerance test: This test can help diagnose acromegaly 4
- Arginine vasopressin levels: This test can help evaluate the patient's hydration status and diagnose diabetes insipidus 4
Imaging Studies
Imaging studies, such as MRI or CT scans, may be ordered to visualize the pituitary gland and diagnose a pituitary mass 3, 6