Human chorionic gonadotropin is usually considered the pregnancy hormone, although even women who are not pregnant produce small amounts. Women transitioning into menopause often have higher levels of hCG than the average woman, making the hormone a useful marker for the life change. This can also, however, lead to an interesting side effect: a false positive on a pregnancy test.
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The Pregnancy Hormone
There are different types of hCG, but perhaps the best known is the type produced by the placenta during the first trimester of pregnancy. HCG shows up in the urine and the blood, and can indicate that a woman is pregnant as well as how her early pregnancy is progressing. A woman who is not pregnant has less than 5 mIU/ml hCG in her blood, while a woman in her third month of pregnancy may have nearly 290,000 mIU/ml, according to the American Pregnancy Association. After menopause, the APA reports, a typical hCG level is just under 10 mIU/ml, although this can vary based on age and levels of other hormones in a woman's body.
Menopause occurs later in a woman’s life, and signifies the end of her reproductive capabilities. Perimenopause is the time leading up to the change, while postmenopause indicates the transition is complete. The perimenopausal period was defined by researchers in a 2005 article in “Clinical Chemistry” as 41 to 55 years of age, and postmenopausal as 55 years and older. Estrogen and progesterone production begin to change as women approach menopause, altering both the menstrual cycle and the number of eggs the ovaries produce each month. A number of physical symptoms may also accompany early menopause, including hot flashes, changes in breast tissue and increased belly fat.
Pregnancy or Perimenopause?
One of the challenges of testing hCG levels in perimenopausal women, says the “Clinical Chemistry” research team, is determining what levels are a result of pregnancy and what changes are a result of the expected hormonal shift. At 5 mIU/ml or more, a woman may test positive for pregnancy, although the APA reports she is not "officially" pregnant until the number passes 25. Some women studied by the team who were not pregnant but fell into this age group measured upwards of 14 to 15 mIU/ml of blood hCG. In other words, a woman in her early 40s who has missed her period could get a false positive on a pregnancy test. Some early menopause symptoms even mimic the signs of pregnancy, including mood swings and weight gain.
HCG and Perimenopause
If you fall into the perimenopausal age range, your other hormone levels may change along with that of your hCG. FSH, or follicle-stimulating hormone, also increases with age. Unexpectedly high levels of both may indicate menopause versus pregnancy. In addition, hCG levels increase significantly during the first few weeks of pregnancy, and according to APA tend to double every few days. If your hCG levels remain steady, you are likely not pregnant but heading toward menopause. If you are uncertain whether your missed period is the result of pregnancy or menopause, don’t put all of your hopes on a pregnancy test: the result may not be what it appears.