Endocrinology: hormones, adenoma hypophysis, pituitary tumor

Human Chorionic Gonadotropin (hCG) is the "pregnancy hormone" or "announcer of pregnancy" that keeps the corpus luteum producing progesterone when you conceive. It is produced by the placenta during pregnancy and is measured by home pregnancy tests (HPTs). A woman normally produces 25 milli-international units per milliliter (mIU/ml) of Human Chorionic Gonadotropin (hCG) 10 days after conception. As a general rule, Human Chorionic Gonadotropin (hCG) levels should double every two to three days after conception. Accordingly, the concentration of Human Chorionic Gonadotropin (hCG) rises rapidly, frequently exceeding 100 mIU/ml by the first missed menstrual period and peaks in the range of 30,000-200,000 mIU/ml by 8-10 weeks into pregnancy. A Human Chorionic Gonadotropin (hCG) level of less than 5 mIU/ml generally indicates that one is not pregnant.

There is great variation in Human Chorionic Gonadotropin (hCG) levels. It isn't the absolute value that matters in these results, but the change in values. In a normal pregnancy, the level of this hormone approximately doubles about every two days during the first 10 weeks. However, high levels of Human Chorionic Gonadotropin (hCG) may indicate choriocarcinoma of the uterus, ectopic pregnancy, Downs syndrome in fetus, hydatidiform mole of the uterus, normal pregnancy, or ovarian cancer. Once you have had an ectopic pregnancy, you have an increased risk for another, so your HCG numbers may be monitored more carefully.

Normal Human Chorionic Gonadotropin (hCG) levels:

0-1 week: 0-50 IU/L
1-2 weeks: 40 - 300
3-4: 500 - 6,000
1-2 months: 5,000 - 200,000
2-3 months: 10,000 - 100,000
2nd trimester: 3,000 - 50,000
3rd trimester: 1,000 - 50,000
Non-pregnant females: < 5.0
Postmenopausal: < 9.5

Higher than Average Human Chorionic Gonadotropin (hCG) levels and what they may indicate:

Molar pregnancy
A molar pregnancy is an abnormality of the placenta, caused by a problem when the egg and sperm join together at fertilization. It is marked by high levels of Human Chorionic Gonadotropin (hCG). Molar pregnancies rarely involve a developing embryo, and the growth of this material is rapid compared to normal fetal growth. It has the appearance of a large and random collection of grape-like cell clusters.

Choriocarcinoma of the uterus
This is the malignant variant of molar pregnancy which metastasizes early by the blood route and is treated by chemotherapy. It is marked by high levels of Human Chorionic Gonadotropin (hCG).

Ectopic pregnancy
If your Human Chorionic Gonadotropin (hCG) level increases but is less than double the previous one then it is considered abnormal and suspicious of an ectopic pregnancy. An ectopic pregnany is a condition where the embryo grows outside the uterus.

Twins or Higher Pregnancies
Twin pregnancies also tend to show higher Human Chorionic Gonadotropin (hCG) levels. Twin Human Chorionic Gonadotropin (hCG) levels fall within the reported range of singletons, so, you can't assume anything based on the level alone. A higher level on a given day does increase your chances for twins, but there's no level above which you're guaranteed twins.
Injections
If you have been given an Human Chorionic Gonadotropin (hCG) injection (Profasi, Pregnyl) to trigger ovulation or to lengthen the leutal phase of your cycle, trace amounts can remain in your system as long as 10 days after your last injection. These can give you high Human Chorionic Gonadotropin (hCG) levels. Two consecutive quantitative Human Chorionic Gonadotropin (hCG) beta blood tests can circumvent this problem; if the level increases by the second test, you are likely to be pregnant.