Human Chorionic Gonadotropin (HCG) is a glycoprotein hormone naturally produced by the placenta during pregnancy, often called the “pregnancy hormone.” HCG is structurally and functionally similar to Luteinizing Hormone (LH), a pituitary hormone central to reproduction in both sexes. HCG acts as an analog to LH, binding to the same gonadotropin receptor (LHCGR) in the ovaries and testes. This action triggers the production of sex hormones, making HCG a prescription medication used to treat specific forms of infertility and hormone deficiencies.
HCG in Female Reproductive Medicine
The primary application of HCG medications in female reproductive medicine is to induce final egg maturation and ovulation, a process often called the “trigger shot.” This is a key step in fertility treatments, including ovulation induction cycles and Assisted Reproductive Technology (ART) procedures like in vitro fertilization (IVF). HCG is typically administered by injection after ovarian stimulation to develop multiple mature follicles.
The HCG injection mimics the natural surge of Luteinizing Hormone that precedes ovulation. By activating LH receptors on the ovarian follicles, HCG signals the eggs to complete their final maturation phase. Ovulation, the release of the mature egg, occurs approximately 38 to 40 hours after the injection.
In IVF cycles, egg retrieval is precisely timed to occur between 34 and 36 hours after the HCG trigger shot, ensuring the recovery of fully mature eggs for fertilization. Medications containing HCG, such as Pregnyl and Novarel, are derived from the urine of pregnant women, while modern recombinant versions (r-HCG) are created in a laboratory setting.
HCG in Male Endocrine and Reproductive Therapy
HCG medications have approved applications in male endocrinology, primarily treating hypogonadotropic hypogonadism. This condition occurs when the pituitary gland does not produce enough LH to stimulate the testes. HCG stimulates the Leydig cells within the testes, prompting them to produce testosterone necessary for maintaining male characteristics and supporting sperm production. HCG is often the preferred treatment for hypogonadism in men who wish to preserve fertility, as it directly stimulates the testes to produce the necessary testosterone for spermatogenesis. Unlike external testosterone replacement therapy, HCG helps maintain testicular function and size.
Treatment protocols involve HCG injections, often given multiple times per week, to restore testosterone levels and achieve adequate sperm counts. Another approved pediatric use for HCG is the treatment of prepubertal cryptorchidism, where one or both testicles fail to descend into the scrotum. The hormone is administered to stimulate the testes, potentially helping them move into the scrotum. This use is typically reserved for boys over four years old and helps determine if surgical intervention, called orchiopexy, will be necessary.
Distinguishing Approved Medical Use from Misapplication
While HCG is a prescription drug, it is frequently associated with non-approved applications, particularly the popular “HCG diet.” This protocol involves taking HCG, often via over-the-counter drops or pellets, while severely restricting calorie intake to 500–800 calories per day. The U.S. Food and Drug Administration (FDA) has not approved HCG for weight loss and actively warns consumers against these products. Scientific consensus confirms that any short-term weight loss is solely due to the drastic calorie restriction, not the HCG itself. Furthermore, these extreme low-calorie diets pose risks, including malnutrition, electrolyte imbalance, and gallstone formation.
HCG is also sometimes misused for performance enhancement by athletes or bodybuilders who use anabolic-androgenic steroids (AAS). Steroid use suppresses the body’s natural testosterone production, which can lead to testicular atrophy. Users administer HCG, often during or after a steroid cycle, to mimic LH and stimulate the testes to restore natural testosterone production and testicular size. This is an unapproved, off-label application that lacks medical supervision and carries inherent risks.