What is Human Chorionic Gonadotropin (hCG)? What Role Does it Play in Pregnancy?

What is Human Chorionic Gonadotropin?

Human chorionic (placenta) gonadotropin (HCG) is commonly known as the pregnancy hormone and consists of two subunits (alpha and beta). The alpha subunit is identical to hormones produced by the pituitary (an organ in the brain) known as follicle stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH are necessary for ovarian egg development and release at the time of ovulation. Both men and women depend on FSH and LH for fertility; men for testosterone and sperm production; women for estrogen, progesterone, and egg release. Gonadotropin means ‘gonad’ or ovary or testes and ‘tropin’ means ‘to promote growth.’ The beta subunit is the portion detected in a urine pregnancy test.

The early placenta produces HCG after the fertilized egg implants in the uterus. Once a blood supply is established with the mother’s, levels of HCG can be detected in urine and blood 8-10 days after conception (fertilization of the egg).

During the early pregnancy, HCG helps the egg sac that already released the egg (corpus luteum) to produce progesterone that helps the early placenta in establishing a good blood supply with that of the mother’s uterus. The placenta takes over the production of progesterone around 14 weeks gestation.

HCG is thought to play a role in mother’s immunity, making her less likely to reject the placenta/pregnancy/baby as foreign since only half of the genetic material came from her. It does this by causing immune cells such as the T cells to become inactive or die near the placenta, allowing it to establish a good blood supply. HCG also suppresses inflammation from the immune cells.

HCG levels start to decline between 2 and 3 months, while estrogen and progesterone continue to rise. HCG and elevated estrogen levels are believed to be the cause of morning sickness.


The Hormone of Pregnancy

There are 4 major tests to detect the beta subunit of HCG, and some can detect very low levels, but they generally take longer to conduct. Blood tests are positive before urine tests. There are 25 home pregnancy tests on the market, and all have different cutoffs for a positive result with 100 being the lowest level detectable in the majority of tests. A positive result for a normal pregnancy can be detected as early as week 4 since the last menstrual period.

Specific structures of the pregnancy can be seen on ultrasound at certain levels of HCG; 2500mIU/ml with the yolk sac which is a structure that feeds the early pregnancy, the baby—called embryonic pole at 5000 mIU/ml, and a heartbeat at 10,000mIU/ml. During early pregnancy, HCG levels double almost every two days. If the levels decrease or stay the same, then this is not a healthy pregnancy and could indicate a tubal pregnancy or an imminent miscarriage. If the level reaches 2000mIU/ml and there is no gestational sac, careful ultrasound evaluation of the ovaries and tubes is necessary because tubal pregnancies can cause a tubal rupture, leading to excessive bleeding, even death. Either surgery or medications can be used to treat ectopic pregnancies, but the HCG levels need to be monitored to see that they return to less than 5mIU/ml.


Side Effects of hCG

There are more side effects of HCG due to the increase in estrogen levels and androgen levels—or testosterone. Estrogen levels can result in breast enlargement in both men and women. Water retention elevated blood pressure, and possible fat deposition are a few other estrogen-related effects. The androgenic side effects are increased oil in the skin, acne, hair growth, and possibly male pattern baldness. The estrogenic side effects can be minimized with the administering of an aromatase inhibitor that prevents the conversion of testosterone into estrogen. Today, HCG is used for hypogonadism (testicular dysfunction), and undescended testicles in males and infertility in females due to low levels of FSH and LH since one subunit of HCG is identical to their respective FSH and LH subunits.

Besides being produced by the placenta, HCG can come about due to other non-pregnant conditions. They are:

  • Phantom HCG- made by weird antibodies
  • Pituitary HCG-seen in postmenopausal women
  • Externally administered HCG- during infertility treatments or for weight loss.
  • Cancers related to pregnancy-molar pregnancy
  • Non-pregnancy related cancers such as stomach, uterine, testicular, pancreas, and liver


Functions of hCG

In its natural state, HCG helps to promote the health of the fetus.

What is HCG
Image Source: Wikipedia

This includes protection from undesirable immune reactions on the part of the mother that may be detrimental to the survival of the fetus. The hormone hCG also helps the corpus luteum to produce progesterone during the early stages of pregnancy.

Another of the roles hCG has is in pregnancy is to make it possible for stored fat to be used in order to nourish the developing baby, ensuring correct growth and development.


Uses of hCG (Supplemental)

Uses of hCG in the form of supplementary injections, drops or tablets include the treatment of infertility and delayed sexual development in boys suffering from pituitary disorders. It is used to monitor the health of women after miscarriage as well as being a tumor marker in certain types of cancer. The measurement of hCG levels is used in certain pregnancy tests, although doctors warn that one test usually isn’t enough to be conclusive.

There are also claims that it can be of help in weight loss by promoting the burning of fat and by reducing the appetite of patients on low-calorie diets. This application remains popular despite considerable controversy.


Types of Supplemental hCG

Prescription hCGInjection Syringe

The hCG injection is preferred by most health care practitioners although various other formulations are available. Drops, creams, tablets and nasal sprays are also on the market. Some doctors contend that hCG is not likely to be absorbed in the digestive system and recommend repeat visits for intra-muscular injections instead.


Homeopathic hCG

Homeopathic treatments are highly diluted yet, according to many users and some doctors, highly effective for weight loss. Despite the low risk factor associated with taking small concentrations of hCG, the FDA has intervened in over the counter sales – an unprecedented move in the field of homeopathy.



  1. Olson TG, Barnes AA, King JK. Elevated hCG Outside of Pregnancy – Diagnostic Considerations and Laboratory Evaluation. Obstet Gynecol Survey. Oct 2007. 62(10):669-74.
  2. Valenzuela R, Iserson KV, Punguyire D. False-positive urine pregnancy tests – clinicians as detectives. Pan Afr Med J. 2011. 8:41. [Full Text].
  3. Cole LA. The utility of six over-the-counter (home) pregnancy tests. Clin Chem Lab Med. 2011 Aug. 49(8):1317-22.
  4. Lijesen GKS, et al. “The effect of human chorionic gonadotropin (HCG) in the treatment of obesity by means of the Simeons therapy: a criteria-based meta-analysis” Br J Clin Pharmacol1995; 40: 237-43
  5. https://www.medscape.com/viewarticle/473515
  6. https://www.medscape.com/viewarticle/775171