A 40 year old lady with temporal field defects and glactorrhoea is most likely to have-
adenoma of the pituitary gland causing increased secretion of prolactin resulting in galactorrhea and causes CNS compression causing temporal field defects (Harrison 17 pg 2206)
Pituitary macroadenoma
Craniopharyngioma
Lactational failure
Pregnancy
Endocrinology