Borderline low progesterone refers to a blood progesterone level which is just below the level expected. It is most commonly diagnosed in women who are pregnant where progesterone is needed for a healthy pregnancy and where low progesterone levels can lead to miscarriage. During menopause, progesterone levels also decrease, but this is a natural phenomenon that is expected.
Progesterone
The Oxford Textbook of Medicine states that progesterone is part of a group of female sex hormones called progestogens, which carry out a number of functions in the body both during the menstrual cycle and during pregnancy. It is formed from cholesterol in the ovaries and in the placenta during pregnancy by a series of chemical reactions. The progesterone synthesis pathway also produces cortisol, the human stress hormone.
Progesterone and The Menstrual Cycle
Progesterone is produced during the luteal phase of the menstrual cycle, the stage just after ovulation has occurred. Here, its primary role is to ensure that your uterus wall is maintained in case a fertilized egg implants and at this stage levels of around five to 20 ng/ml are expected, as stated by the American Pregnancy Association pregnancy guidelines. Once it is clear that there is no fertilized egg after ovulation, progesterone levels drop and the wall is shed, resulting in menstrual bleeding. Levels in this phase will be much lower at around 1ng/ml.
Progesterone in Pregnancy
According to J. Kimball at Harvard University, progesterone is continuously produced during pregnancy, and it is essential to maintain a viable pregnancy. It works together with another female sex hormone called estrogen to ensure that the uterus wall stays intact and receives ample blood to sustain the embryo. The progesterone is produced in response to a hormone from the embryo called human chorionic gonadotrophin. This ensures that the corpus luteum, a body found in your ovary if you are pregnant, does not disintegrate and therefore continues to produce progesterone.
Borderline Low Progesterone in Pregnancy
Throughout pregnancy progesterone levels will rise with the ovaries initially producing the hormone until around eight weeks of gestation, when the placenta takes over. According to the National Institute of Health, during the first and second trimester of pregnancy, minimum levels of 10 to 20 ng/ml and maximum progesterone levels of 90ng/ml are normal. In the third trimester levels may drop to around 45ng/ml. Borderline low progesterone levels in the first few months of pregnancy would be around or just below 10ng/ml, although this figure will vary from person to person. If you have low progesterone levels during pregnancy, your doctor may prescribe progesterone in the form of a suppository in the vagina, injections or pills. This is because women who have miscarriages frequently have low progesterone levels, which are not compatible with viable pregnancies.
Progesterone and Menopause
Between the ages of around 45 to 55, most women will go through menopause, a period characterized by symptoms such as hot flushes, irritability, night sweats and difficulty sleeping. The National Institute of Health states that this occurs due to a drop in serum progesterone and estrogen levels so that progesterone levels are lower than 1ng/ml. These hormonal changes have many downstream effects on other hormones, which is why these symptoms appear. Hormone replacement therapy can be effective at reducing symptoms but you must consult your doctor before commencing such treatments, as there may be a chance of adverse side effects such as elevated risks of heart disease and certain types of cancer.
