LGD-4033, also known as Ligandrol, is an investigational drug in a class called selective androgen receptor modulators (SARMs). It was designed to stimulate muscle and bone growth while minimizing the effects that traditional anabolic steroids have on organs like the prostate and liver. It has not been approved by the FDA for any medical use, and it is illegal to sell as a dietary supplement in the United States.
How LGD-4033 Works
Your body’s androgen receptors are what testosterone and similar hormones bind to in order to trigger muscle growth, bone strengthening, and other effects. LGD-4033 binds to these same receptors with very high affinity, but it does so selectively. In animal studies, the compound showed strong muscle-building and bone-protective activity while largely sparing the prostate, which is one of the organs most affected by traditional steroids.
This selectivity is the core idea behind all SARMs. Rather than flooding every tissue in your body with androgenic signals the way injectable testosterone does, LGD-4033 is engineered to preferentially activate receptors in muscle and bone. That said, the exact mechanisms by which androgens increase muscle mass are still not fully understood, and selectivity in animal models does not guarantee the same clean separation in humans.
What Clinical Trials Have Shown
The most widely cited human data comes from a placebo-controlled Phase I trial published in The Journals of Gerontology, which tested LGD-4033 in 76 healthy young men over 21 days at doses of 0.1, 0.3, and 1.0 mg per day. At those low doses, the compound produced increases in lean body mass that were dose-dependent, meaning higher doses led to more muscle gain. No serious adverse effects were reported at any dose level during the trial, and liver enzyme levels stayed within normal ranges.
The compound was originally developed by Ligand Pharmaceuticals. Viking Therapeutics later acquired it and renamed it VK5211, advancing it into Phase II trials for hip fracture recovery and muscle wasting. Development for other potential uses, including osteoporosis and cancer-related muscle loss (cachexia), has been discontinued.
Testosterone Suppression
Even though LGD-4033 is selective, it still interacts with the hormonal feedback loop that controls your body’s natural testosterone production. In the Phase I trial, total testosterone, free testosterone, and sex hormone-binding globulin all decreased in a dose-dependent pattern during the 21-day treatment period. This suppression is essentially your body recognizing that an androgen-like signal is already present and dialing down its own production in response.
Testosterone levels did recover after the drug was discontinued, but this suppressive effect is significant. People using LGD-4033 at the much higher doses commonly sold online (often 5 to 10 mg or more) would experience more pronounced suppression, potentially requiring weeks or longer for natural hormone levels to return to baseline.
Liver Injury and Other Risks
While the Phase I trial at low doses showed no liver problems, case reports tell a different story at the doses people actually take. A report published in the ACG Case Reports Journal described a 32-year-old man with no prior health issues who developed severe drug-induced liver injury after taking 10 mg of LGD-4033 daily for roughly two weeks. He was hospitalized with jaundice, intense itching, fatigue, and dramatically elevated bilirubin levels. A liver biopsy confirmed cholestatic hepatitis with early fibrosis, meaning bile flow was blocked and scar tissue had begun forming.
That 10 mg daily dose was 10 to 100 times higher than what was tested in the clinical trial. This is a critical detail: the doses circulating in the bodybuilding community bear little resemblance to what researchers have actually studied in controlled settings. And because LGD-4033 is sold through unregulated channels, there is no guarantee that what’s on the label matches what’s in the bottle. Independent testing of SARM products has repeatedly found mislabeled doses, contamination with other compounds, or no active ingredient at all.
Legal and Regulatory Status
LGD-4033 occupies an unusual legal gray area that confuses a lot of people. It is not an approved drug, not a legal supplement, and not a controlled substance in the same category as anabolic steroids. The FDA has explicitly stated that LGD-4033 is not a legitimate dietary ingredient, which makes any supplement claiming to contain it an unapproved new drug by default. Companies selling it as a “research chemical” are exploiting a loophole, marketing it with disclaimers like “not for human consumption” while clearly targeting people who intend to take it.
For athletes, the picture is straightforward. LGD-4033 is banned at all times by the World Anti-Doping Agency under the category of “Other Anabolic Agents.” This applies in and out of competition. The U.S. Anti-Doping Agency has flagged it specifically, noting that athletes have tested positive after unknowingly taking contaminated supplements that contained undisclosed SARMs.
Why People Use It Anyway
LGD-4033 gained popularity in fitness communities because it promises steroid-like muscle gains in a pill, without injections and with fewer side effects. The early clinical data showing lean mass increases at very low doses fueled interest, and underground suppliers quickly began offering it at much higher doses. Online forums are full of self-reported “cycles” where users take 5 to 10 mg daily for 8 to 12 weeks, often stacking it with other SARMs.
The appeal makes sense on the surface, but the gap between what’s been studied and what’s being used is enormous. The only controlled human data covers doses up to 1 mg for 21 days. Everything beyond that is essentially self-experimentation with an unapproved drug of uncertain purity, at doses associated with serious liver damage in at least some users. The long-term effects of repeated cycles remain completely unknown because no study has examined them.