A 35-year-old mother of two children, aged 5 and 6 years has had amenorrhoea and galactorrhoea for the past 12 months. Her serum prolactin level is 450 ng/ml. The most likely diagnosis is

In patients with both galactorrhea and amenorrhea, approximately two-thirds will have hyperprolactinemia; of those, approximately one-third will have a pituitary adenoma. A prolactin level as high as 150-200 ng/mL is almost always due to a pituitary adenoma. Sheehan's syndrome is characterised by amenorrhea and lactation failure (not galactorrhea)