A middle aged female presents with increasing visual loss, breast enlargement and irregular menses. Investigation of choice would be:
A middle aged female is presenting with:

Increasing visual loss
Breast enlargement
Irregular menses

All these features can be explained by pituitary adenoma.

Most common type of pituitary adenomas prolactinomas
Prolactinomas can be diagnosed by raised serum prolactin levels so, the investigation of choice here is serum prolactin level

Also Known: Work up of patient with amenorrhea, galactorrhea, and hyperprolactinemia
S. calcitonin
S. prolactin
S. hemoglobin concentration
S. calcium