A 28 Year Old Female Presents For Complaints Of Fatigue, Increased Sleeping, And Weight Gain.

A 28 year old female presents for complaints of fatigue, increased sleeping, and weight gain
She states she has had depression off and on since she was 17
She denies any other health problems and has never taken any prescription medication, including anything for depression
What are your differentials? What laboratory tests could you perform? How would be your treatment plan?