Investigations

Beta hCG to rule out pregnancy

Prolactin level to rule out prolactinoma

Testosterone and dehydroepiandrosterone sulfate (DHEAS) to rule out hyperandrogenism

FSH and LH for hypothalamic amenorrhea

Pelvic ultrasound

Progesterone challenge test in which Progesterone is administrated to the patient in the form of intramuscular injection and after progesterone is withdrawn. If bleeding takes place within 2 to 7 days, the cause must be the anovulation, but if no bleeding takes place after progesterone withdrawal, the causes are other than anovulation or premature ovarian failure.