• Physiologic causes, renal failure, parasellar tumors, hypothyroidism & 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 (w/ physiologic causes & drug-induced causes ruled out) usually indicates prolactinoma
  
  • A prolactinoma is less likely w/ 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 & 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) w/ gadolinium enhancement is the imaging study of choice
  
  • Computed tomography (CT) w/ 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 w/ large pituitary mass usually indicates hyperprolactinemia secondary to stalk compression
  • Magnetic resonance imaging (MRI) & computed tomography (CT) scan normal & no obvious cause, patient is said to have idiopathic hyperprolactinemia

• 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 & 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)