What causes PCOS?

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Researchers and health care providers do not know what causes PCOS at this time.
Because the symptoms of PCOS tend to run in families, the syndrome is probably caused, at least in
part, by a change (or mutation) in one or more genes.  However, because of the complex pattern of
how PCOS symptoms change from one generation to the next, gene mutations are probably not the
only cause of PCOS.
It is likely that PCOS results from a combination of factors, including genes and environmental features.
Recent research conducted in animal models also suggests that, in some cases, the origins of PCOS
may occur in the womb

Ovulation is the term used to describe the process of releasing a mature egg from the ovary for fertilization or pregnancy.  A woman’s body goes through this process about every 24 to 32 days if she is not pregnant.
In general, ovulation involves the following body parts:
•  Hypothalamus (pronounced high-poe-THAL-amus)—the part of the brain that functions as the main control for the body’s reproductive system.  The hypothalamus works like a thermostat in a furnace in that it controls the levels of different hormones—chemicals that control functions in the body—and other chemicals in the body.  Some hormones get functions going in the body; other hormones cause functions to stop.
•  Pituitary (pronounced pitt-OO-ih-terry) gland—the body’s master gland.  The pituitary sends out hormones to control the other glands in the body, including the ovary (see below).
•  Ovaries—the source of eggs in a woman’s body.  The ovaries have follicles, which are small clusters of cells with a hollow space in the center, in which eggs mature.  The ovaries also make hormones—such as estrogen and androgens—to maintain a woman’s health.
•  Uterus—where a woman carries a baby, also called the womb.  The uterus has different layers; its innermost layer or lining is called the endometrium—endo means “inside” and metrium (pronounced MEE-tree-um) means “womb.”  The endometrium functions as a bed for an embryo when a woman is pregnant.  If no pregnancy occurs, then the endometrium is shed as a menstrual flow, or period.These parts interact with one another to coordinate a woman’s monthly menstrual cycle.
•  The hypothalamus keeps track of the level of natural estrogen in the woman’s body.
•  When the level gets low, the hypothalamus sends an order to the pituitary gland telling it that the body
needs more estrogen


•  The pituitary gets the order and responds by sending out follicle-stimulating hormone (FSH), a hormone
that causes the ovarian follicles to grow and mature, and luteinizing hormone (LH), a hormone that
directs the ovary to make hormones such as estrogen and androgens.  Mature follicles make estrogen
and other substances.  The pituitary continues to make FSH until the mature ovarian follicles make
enough estrogen.  If the follicles don’t make enough estrogen, the level of FSH goes even higher.
•  When the level of estrogen gets high enough, the hypothalamus and pituitary know that there is an egg
ready to be released from a mature follicle.  To get this egg to the uterus so that it can be fertilized, the
pituitary sends out a large burst of LH.
•  LH breaks open the mature follicle to release the egg, allowing it to move toward the uterus.  The level
of LH is only high during the time an egg is being released.  This burst is the basis for home ovulation
detection kits.
•  The empty follicle then starts making progesterone, the hormone that prepares the uterus for
pregnancy.  Increased levels of progesterone cause the endometrium to change in preparation for
pregnancy, should it occur.  Once the endometrium is properly prepared, it can support an embryo and
allow the embryo to grow.
•  If the egg is fertilized, it sends out a hormone called human chorionic gonadotropin (HCG) to let
the body know that it’s there.  HCG is similar to LH and causes the empty follicle to keep making
progesterone, the hormone needed for pregnancy.  Pregnancy tests measure the level of HCG.  If HCG
is present, then it’s likely that a woman is pregnant.
•  If there is no signal, that is, no HCG is present because the egg wasn’t fertilized, the empty follicle
stops making progesterone.  Without progesterone, the endometrium starts to break down, and the
woman’s body sheds it as her menstrual period.  Then the cycle begins again.

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