The aim of this study is to investigate whether inhibition of serum prolactin levels below normal range during cabergoline administration may reduce the recurrence rate after drug withdrawal in patients with prolactinomas.

Prolactinoma patients will be assigned to a experimental group that maintains serum prolactin levels below 5 ng/mL and a control group that maintains normal serum prolactin levels. After that, cabergoline will be maintained at a therapeutic dose for 130 weeks. After cabergoline is discontinued, patients will be followed up with serum prolactin measurement for 52 weeks.

Inclusion Criteria:

• Adults, male or female aged 19 years or older
• diagnosed with prolactinoma
• No previous history of surgery, medication, or radiation therapy

Exclusion Criteria:

• Invasive prolactinomas except invading cavernous sinus
• Taking dopaminergic medications
• Taking medications that can affect serum prolactin level (including estrogenic hormone, oral contraceptive drugs, intrauterine devices)
• Hyperprolactinemia due to secondary causes
• History of pituitary apoplexy within the last 3 months
• Patients with mental illness that should avoid dopamine agonists
• Patients with history of cardiac valve diseases
• Patients with history of pulmonary fibrosis, retroperitoneal fibrosis, and cystic fibrosis
• Moderate degree of hepatic or renal insufficiency (IDMS Modification of Diet in Renal Disease glomerular filtration rate (MDRD GFR) <45 ml/min/1.73m2)
• Patients with cabergoline hypersensitivity reaction
• Pregnant or breast feeding patients