Hyperprolactinemia Diagnosis
Evaluation
- Physiologic causes, renal failure, parasellar tumors, hypothyroidism and drug-induced hyperprolactinemia should be ruled out before extensive evaluation
Measure Fasting Prolactin (PRL) Level
- Normal range: <30 ng/mL normal fasting prolactin (PRL) level
- Diagnostic range: >250 ng/mL (with physiologic causes and drug-induced causes ruled out) usually indicates prolactinoma
- A prolactinoma is less likely with prolactin (PRL) level <100 ng/mL
- Several measurements should be made to confirm diagnosis
Radiologic Evaluation
- Should be performed if there is no obvious cause of hyperprolactinemia and if tumor is suspected
- Physician must decide whether a radiographic study is warranted if prolactin (PRL) level <250 ng/mL but >100 ng/mL
- Magnetic resonance imaging (MRI) with gadolinium enhancement is the imaging study of choice
- Computed tomography (CT) with contrast may also be used
- Serum prolactin (PRL) >200 ng/mL indicates prolactinoma
- Prolactinomas are classified as macroadenoma if the size is ≥10 mm; microadenoma if <10 mm in size
- Serum prolactin (PRL) <200 ng/mL with large pituitary mass usually indicates hyperprolactinemia secondary to stalk compression
- Magnetic resonance imaging (MRI) and computed tomography (CT) scan normal and no obvious cause, patient is said to have idiopathic hyperprolactinemia
Laboratory Tests
- To establish the diagnosis of hyperprolactinemia, it is recommended to have a single measurement of serum prolactin
- A level above the upper limits confirms the diagnosis
- Careful history and physical exam including cranial nerve examination
- Check for galactorrhea, visual field defects, signs of cirrhosis, hair growth pattern on the body, etc
- Drug history
- Blood chemistry [blood urea nitrogen (BUN), creatinine]
- Other pituitary hormones (eg testosterone levels, cortisol, insulin growth factor-1) as necessary
- Pregnancy test
- To rule out macroprolactinemia, polyethylene glycol precipitation is recommended
- Thyroid function tests (to rule out hypothyroidism)