MRI versus CT

Can someone tell me if the MRI and CT analyze the same things, or are they different? 

I ask because my MD recently did an MRI to look at pituitary issues (severe migraines that wake me in the middle of the night about 12 nights per month during menses, plus a myriad of chronic endocrine diseases) and the results showed normal pituitary (the only abnormality was a maxilliary retention cyst behind the right eye). 

Would a CT only be repetitive or would it discriminate different issues versus the MRI?    I am taking depakote, maxalt, frova, fioricette and halcion, but nothing helps during the early morning bouts of severe headache, nausea, (and vomitting if remain seated or laying down). THank you for any and all insights.