A 30 year old woman presents with secondary amenorrhoea and galactorrhoea for 3 years. Which of the following is the most likely diagnosis?

Prolactinoma is a tumor arising from lactotrope cells of pituitary. Women usually present with amenorrhea, infeility, and galactorrhea. If the tumor extends outside the sella, visual field defects or other mass effects can occur. Diagnosis of prolactinoma is likely with a PRL level >200mg/L. Oral dopamine agonists (cabergoline and bromocriptine) are the mainstay of therapy for patient with micro or macroprolactinomas. They suppress PRL secretion and synthesis as well as lactotrope cell proliferation. Indications for surgical adenoma debulking include dopamine resistance or intolerance, presence of an invasive macroadenoma with compromised vision that fails to improve after drug treatment. Ref: Harrison's Internal Medicine, 18th Edition, Pages 2261-2263, 2888, 3388 and 3389, Chapter 339