Estradiol, the main human estrogen, is about 100 times higher than normal. Estriol, the weakest form of human estrogen and the estrogen that is dominant in pregnancy, rises to about 1,000 times the normal level. As estrogen rises, other hormones, such as thyroid and cortisol, also rise. However, most of the excess is bound by protein and nonusable. This binding prevents women from becoming hyperthyroid or having adverse effects from too much cortisol The high levels of hormones normally make pregnant women feel wonderful.
Women frequently say their health was better during pregnancy than any other time of their life.
The high hormone level acts similar to steroids and, consequently, women with a collagen disease or arthritis may lose their symptoms while pregnant. On the other hand, hormonal dysfunction during pregnancy can leave a woman feeling nauseated and ill, leading to such pregnancy complications as high blood pressure, preeclampsia, toxemia, breakthrough bleeding, and premature labor. At about the twelfth to sixteenth week, the placenta develops, and it begins to produce hormones, including a number of hormones only found in pregnant women. So the placenta tends to suppress or override pituitary function during pregnancy. A woman s high level of hormones during pregnancy is a cooperative effort by mother, placenta, and fetus.