Overview
Ever wondered how your body knows you’re pregnant even before you do? Meet the Human Chorionic Gonadotropin, the pregnancy hormone! A key player behind the success of an IVF process. But how does it do that? Why and how is it formed during pregnancy? This article answers all these questions. So, let’s get started!
Introduction
HCG hormone is essential to reproduction and is one of the first hormones produced once a woman conceives. It helps the body develop the right environment for the embryo to grow. Beyond confirming a pregnancy, hCG is sometimes administered in fertility treatments such as IVF (In Vitro Fertilisation), and is sometimes used to balance hormonal deficiencies. Assessing hCG levels in both natural conception and assisted reproduction can provide detailed information about the progression of the pregnancy and assess reproductive health.
What is hCG?
Human Chorionic Gonadotropin (hCG) is a glycoprotein hormone which is produced in the early stages of pregnancy. It is made by the cells which form the placenta, the organ responsible for providing oxygen and nutrients to the growing baby. It appears in the blood and urine of pregnant women about 10 days after fertilisation, eventually leading to positive pregnancy tests.
The primary function of hCG is to support the Corpus Luteum, which is a structure within the ovary that secretes progesterone. Progesterone is necessary to maintain the uterine lining during early pregnancy; therefore, without hCG, early pregnancy would not be sustained.
Interestingly, hCG is not limited to women, as it is commonly used in men as a treatment to increase testosterone production and to promote sperm production as part of fertility treatments.
What is the Function of hCG in the Body?
Though it is referred to as the pregnancy hormone, hCG serves a much broader role than simply confirming the pregnancy. It serves as a sign for the body to switch from a relaxed to a supportive environment for the new growing human inside it, by:
- Supporting the Corpus Luteum: hCG allows for the corpus luteum (a temporary gland formed after ovulation) to stay intact. This gland secretes progesterone, a hormone required for maintaining the uterine lining and supporting early pregnancy.
- Supporting Placental Development: hCG stimulates the growth of blood vessels in the uterus, providing nutrients and oxygen to the developing embryo.
- Regulating Hormonal Balance: hCG works to regulate the levels of other hormones like oestrogen and progesterone during a healthy pregnancy.
- Preventing Menstruation: hCG allows progesterone to be produced at a sufficient level to stop the menstrual cycle and protect the uterine lining, allowing conception to occur.
- Promoting Organ Development of the Foetus: hCG indirectly promotes early foetal organ development by stabilising maternal hormone levels and facilitating nutrient exchange during pregnancy.
So, in simple terms, hCG is kind of a guardian angel which safeguards your growing child in the early stages of pregnancy.
HCG levels and Pregnancy
Since Human Chorionic Gonadotropin is produced predominantly by the placenta, the levels of hCG are very low or even undetectable in Non-pregnant women. In fact, for women who are not pregnant, the presence of hCG can indicate some rare but serious conditions, such as hormonal imbalance or tumours.
On the other hand, hCG levels in a healthy pregnancy rise quickly after fertilisation, when the embryo implants in the uterine wall, often doubling every 48 to 72 hours during the first few weeks. Consequently, most pregnancy tests rely on this rapid increase to confirm pregnancy.
Normal hCG levels during Pregnancy:
| Pregnancy Stage (Calculated From Last Menstrual Period) | hCG Reference Range (mIU/mL) |
|---|---|
| Non-Pregnant Women | < 5 |
| 3 Weeks | 5 – 50 |
| 4 Weeks | 5 – 426 |
| 5 Weeks | 18 – 7,340 |
| 6 Weeks | 1,080 – 56,500 |
| 7–8 Weeks | 7,650 – 229,000 |
| 9–12 Weeks | 25,700 – 288,000 |
| 13–16 Weeks | 13,300 – 254,000 |
| 17–24 Weeks | 4,060 – 165,400 |
| 25–40 Weeks | 3,640 – 117,000 |
Note that hCG levels do not continue to rise infinitely. HCG levels peak around the 9th to 12th week and then slowly decrease as the placenta takes over hormone production for the remainder of the pregnancy.
How is hCG tested?
Testing hCG consequently means testing for pregnancy, and it can be measured through either of the two ways, which includes:
1. Urine tests:
A urine test checks for hCG. Although it does not measure the exact level, it can detect only the presence of hCG. These tests become more accurate after a missed period, and can be done at home or in your doctor's office.
2. Blood tests
Your healthcare professional takes a small sample of blood from your arm to measure the precise level of hCG in your blood. This test is highly sensitive and can detect pregnancy earlier than a urine test. It also provides a quantitative result, meaning it gives the level as a number.
However, for better confirmation of pregnancy, a prenatal ultrasound is more reliable than these tests.
HCG in Males
Although it is more often associated with females, hCG can also be produced in males in very small amounts to regulate testosterone levels. In males, this hormone is mainly produced by the pituitary gland, unlike females, in which it is produced by the placenta in the uterus during gestation.
The core functions of hCG in men include:
- Regulating the testosterone production by signalling cells of the testes to produce testosterone, eventually controlling sperm production, libido, and secondary sexual characteristics.
- Males with low levels of testosterone hormone or other fertility issues are given hCG injections as a method of treatment.
- Markers of hCG also give a rough idea of potential infertility causes.
What Do Abnormal hCG Levels Indicate?
Abnormal levels of hCG are considered abnormal only with respect to the timing, symptoms, and other diagnostic tests. That is:
Low hCG Levels:
Low levels of hCG may indicate:
- The pregnancy is still in its early stages. In fact, it can also be a result of human error by miscalculating ovulation and implantation dates.
- In serious cases, a falling level of hCG can indicate a miscarriage.
- In some cases, when the levels of HCG are not rising at a normal rate, it can be a signal of ectopic pregnancy.
High hCG Levels:
Higher levels of hCG or a higher rate of increase of hCG can indicate:
- Multiple pregnancies, that is, pregnancy with triplets, twins, or any higher multiples.
- In rare instances, such as molar pregnancy, hCG can grow aggressively.
- Elevated hCG levels can indicate serious masses/pathologies in both men and women.
HCG in Assisted Reproductive Technologies
HCG is a significant hormone associated with assisted reproductive therapies (i.e. IVF, ICSI). In particular, it is commonly used as a trigger shot for both in vitro fertilisation and ovulation induction to facilitate the retrieval of mature eggs. After embryo transfer, hCG is frequently monitored as it is a key sign of implantation and early pregnancy.
Apart from female infertility cases, hCG shots are also administered to men, as these hormones are an integral part of testosterone production in males. This eventually leads to the production of sperm.
When to See a Doctor:
Get tested and consult your healthcare provider for hCG levels if you experience any of these:
- Missed Periods
- Unusual Bleeding during pregnancy.
- Abdominal pain
Conclusion
Finally, hCG is not just a "pregnancy hormone"; it is an important signal that activates the body's early pregnancy mode. From pregnancy confirmation tests to medications in assisted fertility, monitoring hCG levels is a key marker of reproductive health. Both low and high levels can be a sign of trouble, but can also give doctors a 'road map' for prompt treatment. When women and men understand the role of hCG, they can begin to make informed choices, promote healthier pregnancies, encourage successful fertility efforts, and improve reproductive health as a whole.
Common Questions Asked
Can hCG levels vary between pregnancies?
Absolutely. Each pregnancy is different. Levels of hCG can vary significantly from one woman to another.
Does hCG contribute to morning sickness?
High levels of hCG could cause nausea. Some women experience worse morning sickness because of high levels of hCG.
How does exercise affect hCG levels?
Normal activity does not change hCG levels, but if a pregnancy is complicated, then vigorous exercise should be monitored.
How soon can hCG be detected after conception?
In the blood, hCG may be detected approximately 6–10 days post-fertilisation. A urine test may show positive results a few days later.
Is hCG used for losing weight?
hCG injections have been marketed as a weight loss product. However, scientific studies show that hCG is ineffective for weight loss and not recommended.