Nonfunctioning Pituitary Adenomas

Key Features

Essentials of Diagnosis

• Clinical and biochemical evaluation for pituitary hormone hypersecretion is negative

• MRI shows a pituitary microadenoma (<1 cm diameter) or macroadenoma (≥ 1 cm diameter)

• Headache, visual field compromise and anterior hypopituitarism are common with macroadenomas

• Elevated serum PRL with macroadenomas may be due to stalk compression

General Considerations

• Benign neuroendocrine neoplasms that do not produce symptoms from hormone oversecretion

• Nonfunctioning pituitary microadenomas (< 1 cm) are common, detected as an incidental finding in 4–37% of brain CT or MR imaging

• Account for up to 14–54% of all pituitary adenomas and are more frequent with advancing age

Clinical Findings

Symptoms and Signs

• Nonfunctioning pituitary macroadenomas

  • Measure 1 cm or larger

  • Tend to be more aggressive than functioning pituitary adenomas

  • Frequently present with mass effect symptoms, including

    • Headache

    • Visual field compromise

    • Cranial nerve palsies affecting extraocular muscles

    • Pituitary apoplexy

• Larger macroadenomas frequently cause some hypopituitarism, particularly hypogonadotropic hypogonadism

• Nonfunctioning pituitary microadenomas are asymptomatic

Differential Diagnosis

• Pituitary craniopharyngiomas

• Gliomas

• Meningiomas

• Skull base osteosarcomas

• Rathke cysts

• Lymphocytic hypophysitis

• Infection

• Metastases

Diagnosis

Laboratory Findings

• All patients with a pituitary adenoma require testing for pituitary hormone hypersecretion

  • A serum PRL is obtained to screen for prolactin hypersecretion

  • Women with hyperprolactinemia are tested for pregnancy with a serum hCG.

  • Clinical suspicion should dictate whether to formally test for Cushing disease or acromegaly

• Pituitary macroadenomas

  • All patients require evaluation for anterior hypopituitarism

  • Serum free T₄, thyroid-stimulating hormone (TSH), morning serum testosterone and free testosterone (men)

  • Serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) (men with low serum testosterone, women who are postmenopausal, and younger women with amenorrhea)

  • Serum sodium and glucose

  • A serum IGF-I is drawn to screen for growth hormone (GH) deficiency

  • Younger patients with short stature who have not fused their epiphyses should have a full evaluation for growth hormone deficiency

  • Patients with a macroadenoma that impinges upon the optic chiasm require formal visual field testing

  • A cosyntropin stimulation test is performed for patients with hyponatremia or symptoms of possible hypoadrenalism

Imaging

• Pituitary dynamic contrast-enhanced MRI (3T)

  • Modality of choice for the evaluation and follow-up of pituitary adenomas

  • About 10% of nonfunctioning pituitary microadenomas enlarge over several years, whereas 23% of pituitary nonfunctioning macroadenomas enlarge significantly

  • Nonfunctioning pituitary microadenomas that are < 5 mm require no further MRI follow-up

  • For nonfunctioning pituitary adenomas ≥ 5 mm, repeat MRI is recommended at 6 months then yearly for 3 years

  • If no enlargement is noted, MRI surveillance can be done less frequently

Treatment

• No treatment needed for ...