Secondary amenorrhea is lack of periods for 6 or more months in a woman who has already started menstruation and who is not pregnant, breastfeeding, or in menopause.

See also:

• Menstruation - Absent
• Primary amenorrhea

There are many reasons for missing a period. Polycystic ovarian syndrome is a frequent cause of secondary amenorrhea.

You are also more likely to have secondary amenorrhea if you engage in extreme and prolonged exercise, have less than 15 - 17% body fat, are obese, or take hormonal supplements.

Other causes include:

• Sudden significant weight loss as seen with strict dieting or after gastric bypass surgery
• Anxiety and emotional distress
• Thyroid dysfunction
• Brain (pituitary) tumors
• Premature ovarian failure

The following drugs may also cause missed periods:

• Busulfan
• Chlorambucil
• Cyclophosphamide
• Phenothiazines
• Birth control pills
• Hormone therapy such as Depo-Provera

Also, procedures, such as a dilation and curettage (D and C), can lead to scar tissue formation that may cause a woman to stop menstruating. This is called Asherman syndrome.