Human Chorionic Gonadotropin (HCG) is a natural peptide hormone produced by the female body during pregnancy. Its level begins to rise seven days before ovulation, and modern pregnancy tests rely on its detection in urine.

In clinical medicine, isolated HCG is primarily used to:

• Induce **ovulation** in women.
• Treat **underdeveloped testicles (cryptorchidism)** in boys.

For individuals using anabolic hormones (e.g., testosterone and nandrolone derivatives), the most important function of HCG is supporting **Post Cycle Therapy (PCT)**. The hormonal system operates via a negative feedback loop. External administration of sex hormones signals the body to downregulate or completely stop its own natural testosterone production in the testicles.

Action: HCG mimics the action of **Luteinizing Hormone (LH)**, which is responsible for stimulating the Leydig cells to produce testosterone. As a result, HCG helps the testicles regain their original size and function. The faster natural testosterone production is resumed, the quicker the level of catabolic **Cortisol**—which is released in the absence of androgens and promotes muscle loss—can be lowered.

Outdated dosing methods exist (e.g., 5000 IU every 5 days for 3 weeks), which can be ineffective or even harmful. By mimicking LH, HCG can trigger a negative feedback response that, in turn, halts the production of **GnRH** (Gonadotropin-Releasing Hormone)—a necessity for LH production.

Key Principle: Dosing HCG over a prolonged period at high doses provokes **testicular desensitization**, which means the testicles may fail to respond to natural LH in the future.

Modern PCT Strategy:

• Outdated single high doses (e.g., 5000 IU) should be avoided.
• A daily dose of approximately **500 IU over a period of 2–3 weeks** is recommended. This method ensures a more stable level of the active substance and a lower risk of desensitization.
• HCG is typically injected during the last two weeks of the steroid cycle and then suddenly discontinued.
• It is crucial to combine HCG with estrogen receptor blockers (e.g., **Clomiphene and Tamoxifen Citrate**). Estrogen blockade stimulates the hypothalamus to release GnRH, allowing for the planned production of testosterone once the testicles have regained their original size thanks to HCG.

Storage: Reconstituted HCG must be stored **refrigerated** and protected from light to prevent loss of activity.

Side Effects: Include elevated blood pressure, headaches, mood swings, and **increased estrogen levels**. This last effect is mitigated by the simultaneous use of estrogen receptor blockers (Clomiphene/Tamoxifen) during PCT.

Counterfeit Issue: HCG is frequently sold as expensive Growth Hormone (STH/Somatropin) because both dry powders are very similar. However, the counterfeit is relatively easy to detect: the fake Growth Hormone (alleged STH) can be checked with a **pregnancy test**. If the test is positive, it confirms that the user acquired the cheaper HCG substance instead of expensive STH.

Availability: Preparations like Spanish **"HCGlepori"** or Turkish **"Pregnyl"** (available over the counter in some countries, like Turkey) are common. However, always beware of unmarked vials sold as STH.