HCGWhat the studies show

Q: What kind of evidence exists for human chorionic gonadotropin?

Large human trials. An approved prescription hormone with decades of clinical use for fertility and hypogonadism, small controlled studies behind its testosterone-related uses, and controlled evidence against the diet claim.

The pregnancy hormone that acts like a long-lasting pulse of LH, an approved fertility drug for decades — and the subject of a diet claim the evidence rejects.

5 min read · Large human trials · Updated November 2026

In short

Name: human chorionic gonadotropin (sold by Progression Labs as HCG)
Evidence: Large human trials
Bottom line: An approved prescription hormone with decades of clinical use for fertility and hypogonadism, small controlled studies behind its testosterone-related uses, and controlled evidence against the diet claim.

Before you read this

This guide explains what published studies found. That is all it is.

It is not medical advice and it is not instructions for using anything. Where a dose appears, we are reporting what a named study gave the people or animals in it — a fact about the study, not an instruction to you.

The compounds here are not approved by the FDA for use in people and are sold for laboratory research only. A study tells you what happened to the subjects in it; it does not tell you what would happen to you. Talk to a doctor first.

What it is

Human chorionic gonadotropin is a hormone made by the placenta from the first days of pregnancy; it is what a pregnancy test detects. It is a glycoprotein of two chains. Its alpha chain is identical to the one in luteinizing hormone, LH, the pituitary signal that tells the testes to make testosterone and the ovary to release an egg; the beta chain differs, and gives hCG a much longer life in the blood ¹. Because it binds the same receptor as LH, an injection of hCG acts like a long-lasting pulse of LH. It is an approved prescription drug in the United States, sold as Pregnyl and Novarel among other names and extracted from the urine of pregnant women, with three labelled uses: triggering ovulation in women undergoing fertility treatment, undescended testes in boys, and hypogonadotropic hypogonadism in men, where the pituitary fails to send the LH signal ².

The studies below call this molecule human chorionic gonadotropin. Progression Labs sells it as HCG; the guide uses the store's name and the papers use theirs.

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Leydig cells and testosterone

Testosterone is made by the Leydig cells of the testis in response to LH. When a man's own LH is switched off — by pituitary disease, or by testosterone given from outside, which the pituitary reads as a signal to stop — the Leydig cells go quiet and the testes shrink. hCG stands in for the missing LH. In a 2005 study at the University of Washington, 29 healthy men were given weekly testosterone, which shut down their own LH, plus either saline or hCG at one of three doses every other day for three weeks; testosterone inside the testis fell by 94 percent in the saline group and was held or raised in the hCG groups, in proportion to the dose ³. A 2013 series followed 26 men on testosterone therapy who were also given hCG; none became azoospermic and their semen measures were maintained ⁴. Those studies are why hCG appears alongside testosterone in fertility-preserving protocols. That is prescription medicine, decided case by case by physicians, and the studies are weeks long in a few dozen men.

Fertility

In men whose pituitary does not make LH, hCG alone restores testosterone and in many starts sperm production; FSH is added when sperm are the goal. In women, a single injection of hCG stands in for the LH surge that releases an egg, which is why it is the standard trigger before egg retrieval in IVF and in timed ovulation ². These are its labelled uses, and the evidence for them is decades of clinical use rather than one trial.

The hCG diet

In the 1950s a physician named Simeons proposed hCG injections alongside a 500-calorie diet for weight loss, and the idea has never died. A 1995 meta-analysis reviewed 24 studies of the claim and found no evidence that hCG causes weight loss, fat redistribution, less hunger or better well-being beyond what the starvation diet does on its own ⁵. The FDA requires every hCG label to state that it has no known effect on fat mobilization, appetite, hunger or body-fat distribution and that there is no substantial evidence it increases weight loss beyond caloric restriction ². In 2011 the agency added that over-the-counter and "homeopathic" hCG weight-loss products are illegal and unproven ⁶.

Side effects and what is not known

The label lists headache, irritability, restlessness, tiredness, fluid retention and gynecomastia, and in women on fertility treatment ovarian hyperstimulation syndrome, which can be serious; in boys it can bring on early signs of puberty ². Raising testosterone by any route raises the estrogen made from it, which is where the breast-tissue effect comes from. The controlled studies of hCG outside its approved uses are weeks long with a few dozen participants ³, so there is no controlled data on what years of hCG do, and the diet studies, which are the longest, found nothing to show for it ⁵.

What these studies are, and aren't

Large human trials. An approved prescription hormone with decades of clinical use for fertility and hypogonadism, small controlled studies behind its testosterone-related uses, and controlled evidence against the diet claim.