Free testosterone elevation and SHBG reduction
Multiple human RCTs demonstrate Tongkat Ali significantly increases free testosterone by reducing sex hormone-binding globulin (SHBG) — which binds testosterone and renders it inactive. Unlike exogenous testosterone, Tongkat Ali works through the body's own hypothalamic-pituitary-gonadal (HPG) axis, increasing LH-stimulated testicular testosterone production. Studies show 37–122% increases in free testosterone.
Male fertility and sperm quality
Human clinical studies show Tongkat Ali significantly improves sperm concentration, motility, morphology, and DNA integrity in sub-fertile men. A 9-month clinical study showed spontaneous pregnancy rates of 14.7% in the Tongkat Ali group — significant for a population with previously documented infertility.
Athletic performance and body composition
RCTs in trained athletes and active older adults show Tongkat Ali significantly improves muscular strength, lean body mass, and physical performance. Studies show greater gains in lean mass, reduced fat mass, and improved muscle strength compared to placebo when combined with resistance training — consistent with the testosterone-enhancing effects.
Cortisol reduction and stress adaptation
A landmark study in moderately stressed adults showed Tongkat Ali (200 mg/day LJ100®) significantly reduced salivary cortisol by 16%, increased testosterone by 37%, and improved overall mood state — reducing tension, anger, and confusion scores. This cortisol-lowering effect positions Tongkat Ali as a unique adaptogen with both anabolic and anti-catabolic properties.
Libido and sexual function
Multiple clinical studies confirm Tongkat Ali significantly improves libido, sexual function, and erectile function in both men and women. The combination of testosterone enhancement, cortisol reduction, and direct effects on sex hormone receptors produces meaningful improvements in sexual health across age groups.
SHBG inhibition and free testosterone liberation
Eurycomanone and eurypeptides inhibit the binding affinity of SHBG (sex hormone-binding globulin) for testosterone, increasing the fraction of unbound, bioavailable free testosterone without changing total testosterone production rates. This mechanism is distinct from testosterone precursors (DHEA) and direct LH/FSH stimulators.
HPG axis stimulation via LH release
Tongkat Ali bioactives stimulate luteinizing hormone (LH) release from the pituitary gland, which in turn drives Leydig cell testosterone synthesis in the testes. This HPG-axis mechanism produces natural testosterone production increases that stay within physiological ranges — avoiding the suppressive feedback of exogenous testosterone.
5-alpha reductase and aromatase modulation
Tongkat Ali moderately inhibits 5-alpha reductase (preventing testosterone conversion to DHT) and aromatase (preventing testosterone conversion to estradiol), further shifting the hormonal environment toward optimal free testosterone bioavailability in both sexes.
Randomized, double-blind, placebo-controlled trial of LJ100® (200 mg/day) vs. placebo in 63 moderately stressed adults for 4 weeks.
63 healthy but stressed adults. 4-week intervention.
LJ100® significantly reduced salivary cortisol by 16%, increased testosterone by 37%, and improved mood state scores (tension -11%, anger -12%, confusion -15%). Hormonal profile shifted significantly toward anabolic/anti-catabolic balance. No adverse effects.
Prospective study of Tongkat Ali root extract supplementation in 75 male partners of infertile couples for 9 months.
75 sub-fertile men. 9-month supplementation study.
Tongkat Ali significantly improved semen volume, sperm concentration, motility, and morphology. Spontaneous pregnancy rate of 14.7% achieved. Baseline sperm quality parameters all significantly improved from baseline. Supports use in male infertility.
Randomized, double-blind, placebo-controlled trial of Tongkat Ali extract (400 mg/day) vs. placebo in 32 physically active men and women aged 57–72 for 5 weeks.
32 physically active older adults. 5-week intervention.
Tongkat Ali significantly increased muscular force (+16.6%), arm circumference, and free testosterone levels. DHEA increased significantly. Fat mass decreased. SHBG decreased. Particularly meaningful results in an older population where testosterone decline is clinically significant.