amenorrhea

A 45-year-old woman presents to her GP with a 6-month history of irregular menstrual cycles and hot flashes. She also reports mood swings and difficulty sleeping. Her last menstrual period was 3 months ago. What is the most likely diagnosis?

A 28-year-old woman presents to her GP with a 3-month history of amenorrhea. She reports occasional headaches and galactorrhea. She is not on any medications and has no significant past medical history. On examination, her vital signs are normal, and there are no visual field defects. A pregnancy test is negative. What is the most appropriate initial investigation?