Randomised trials of the NAD+ precursors nicotinamide riboside and nicotinamide mononucleotide show they raise NAD+, and two described them as well tolerated. Effects on function were limited: some ventilatory-threshold gains in runners, nominal gait and grip changes, and no change in VO2max or body composition.

A 2025 review found 35 of 36 BPC-157 studies were preclinical. A two-year MK-677 trial raised fat-free mass in older adults but not strength or function, and worsened glucose control.

Ecdysterone, methoxyisoflavone, androstenedione, androstenediol and DHEA all failed to improve strength or body composition over placebo in randomised training trials; prohormones raised oestrogens.

Irritability and aggression during use, depression and suicidality on withdrawal, and a dependence pattern that looks like other drugs. What the clinical literature reports, and what it cannot yet prove.

Surveys and observational studies record stacked anabolic steroids, thyroid hormone, beta-agonists and diuretics at doses far above medical use. What the published record shows, and what it costs.

Two mechanistic studies show what mechano growth factor actually does in mouse muscle and heart, and why the absence of any human trial should settle the question for anyone thinking of buying it.

Testosterone falls about 0.4 percent a year in total and 1.3 percent in free form after 40, yet only 2 percent of men meet strict criteria for late-onset hypogonadism - and 73 percent of those are overweight. What the hormone does for muscle, bone and sex, and what reverses the decline.

Supraphysiological androgens shut down the body's own testosterone, thicken and weaken the heart, and suppress fertility. Recovery of the hormonal axis usually takes 3-12 months, but some effects - gynaecomastia, coronary plaque, incomplete fertility - can persist for years or for good.

Roughly 1 to 5 percent of people worldwide have used anabolic-androgenic steroids, around 5 percent of gym-goers and 25 to 50 percent of competitive bodybuilders. Most users are not competitive athletes at all. What drives the decision, why muscle dysmorphia matters more than sport, and what the evidence says the trade actually costs.

Across 27 studies, growth hormone raised lean mass by about 2 kg - mostly fluid - while strength and VO2max did not improve and lactate rose. Swelling hit 44 percent and fatigue 35 percent. The review's verdict: claims that it enhances performance are not supported. Here is the evidence.

Randomised trials in 9,000 men cleared testosterone therapy of the heart attacks and strokes the databases pinned on it - and convicted it of arrhythmia instead. What that means for confirmed deficiency.