Secondary amenorrhea can occur due to natural changes in the body. For example, the most common cause of secondary amenorrhea is pregnancy. Breastfeeding and menopause are also common, but natural, causes.

Women who take birth control pills or who receive hormone shots such as Depo-Provera may not have any monthly bleeding. When they stop taking these hormones, their periods may not return for more than 6 months.

You are more likely to have absent periods if you:

Are obese

Exercise too much and for long periods of time

Have very low body fat (less than 15% to 17%)

Have severe anxiety or emotional distress

Lose a lot of weight suddenly (for example, from strict or extreme diets or after gastric bypass surgery)

Other causes include:

Brain (pituitary) tumors

Drugs for cancer treatment

Drugs to treat schizophrenia or psychosis

Overactive thyroid gland

Polycystic ovarian syndrome

Reduced function of the ovaries

Also, procedures such as a dilation and curettage (D and C) can cause scar tissue to form. This tissue may cause a woman to stop menstruating. This is called Asherman syndrome. Scarring may also be caused by some severe pelvic infections.