Tumors on the pituitary usually overproduce hormones, not underproduce. Without any evidence of hormone overproduction, there is no need in my non-medical opinion to go through the time and expense of an MRI. Further there is some risk to the dye that is used to stain the gland. And since pituitary tumors are notoriously hard to see on imaging, a 3 Tesla machine is required which further increases the expense. All of those are worthwhile if there is evidence of hormone overproduction, of course. The only thing visible on a pit MRI that could cause AI would be empty sella syndrome which happens after pregnancy/labor. It's possible this is the case, but again, the treatment wouldn't change so I would skip it.