Ingredient Deep Dives
Each active, on the record
Overview, mechanism, research highlights, and quality standard — for every ingredient in the formula.
Ingredient · 01
TestoSurge®
Standardized fenugreek seed extract (Trigonella foenum-graecum)
Overview
TestoSurge® is a patented fenugreek extract from Indus Biotech, standardized for furostanolic saponins — the constituents associated with the hormonal endpoints reported in clinical work on fenugreek.2
Mechanism
Investigated for inhibition of aromatase and 5α-reductase activity, with downstream effects on the free-to-bound testosterone ratio rather than total production alone. Protodioscin content may also support luteinizing hormone (LH) secretion.
Research highlights
Randomized, placebo-controlled trials in resistance-trained males have reported improvements in total and bioavailable testosterone and body composition over 8-week protocols.3 A 2020 meta-analysis pooling four RCTs found a statistically significant increase in total serum testosterone,4 and a 2021 systematic review of 32 RCTs identified fenugreek as one of only two herbs with positive effects on testosterone in men.7
Quality standards
Standardized to ≥ 20% furostanolic saponins. HPLC identity verified.
Research callout
Studied at 500 mg/day in resistance-trained adults.
Reviewed by the 4 Gauge research team
Ingredient · 02
Ashwagandha
KSM-66® Withania somnifera root extract
Overview
A full-spectrum, root-only ashwagandha extract standardized to ≥ 5% withanolides by HPLC — a more rigorous standardization than UV-based testing. Withanolides are the steroidal lactones responsible for ashwagandha's hormonal and adaptogenic effects.8
Mechanism
Modulates the HPA axis. By dampening cortisol output under chronic stress, it relieves a known suppressor of GnRH and downstream testosterone synthesis, while also supporting LH.9
Research highlights
A crossover RCT in aging men reported an 18% greater increase in DHEA-S and a 14.7% greater increase in testosterone vs. placebo,10 and a 12-week RCT showed significant increases in free testosterone and LH.11 Reviews report cortisol reductions of roughly 11–32% alongside favorable testosterone effects in men.13
Quality standards
Standardized to ≥ 5% withanolides by HPLC.
Research callout
Strongest evidence base of any adaptogen for stress-driven hormonal endpoints.
Reviewed by the 4 Gauge research team
Ingredient · 03
Shilajit
Purified Himalayan resin
Overview
A mineral-rich resin from high-altitude rock strata, characterized for its fulvic and humic acid content. 4 Gauge uses shilajit standardized to ≥ 50% fulvic acid by HPLC.14
Mechanism
The fulvic-acid fraction acts as a mineral-shuttling carrier; mechanistic work points to activation of steroidogenic enzymes (3β-HSD and 17β-HSD) and reduced testicular oxidative stress.18
Research highlights
A 90-day randomized, double-blind, placebo-controlled trial in healthy men (250 mg twice daily) reported significant increases in total testosterone, free testosterone and DHEAS, with LH and FSH maintained.15 An 8-week RCT also showed shilajit attenuated fatigue-induced losses in muscular strength.16
Quality standards
Purified resin, fulvic acid ≥ 50%, screened for heavy metals.
Research callout
Use purified resin only — raw shilajit can carry heavy-metal contamination.
Reviewed by the 4 Gauge research team
Ingredient · 04
Vitamin D3
Cholecalciferol
Overview
Vitamin D functions as a steroid-hormone precursor. Its receptor (VDR) is expressed throughout reproductive tissues, including the Leydig cells of the testes.19
Mechanism
Adequate 25(OH)D status supports normal expression of steroidogenic enzymes and may lower SHBG, increasing free testosterone; insufficiency consistently tracks with lower androgen markers.22
Research highlights
A PRISMA systematic review found vitamin D deficiency is associated with lower testosterone and that supplementation may improve it, particularly in deficient men,20 a finding supported by a 2024 meta-analytic review of androgen endpoints.21
Quality standards
Cholecalciferol form, assayed for potency.
Research callout
Test 25(OH)D. Aim for sufficiency, not megadosing.
Reviewed by the 4 Gauge research team
Ingredient · 05
Chelated Zinc
Zinc bisglycinate
Overview
Zinc is a cofactor for over 300 enzymes, including those involved in testosterone biosynthesis. Bisglycinate is selected for tolerability and absorption.24
Mechanism
A required cofactor in androgen production that also inhibits aromatase and supports LH-receptor signalling on Leydig cells. Restricting dietary zinc lowers testosterone in young men within weeks.25
Research highlights
Reviews and clinical work show zinc status is directly linked to serum and seminal testosterone, with repletion most beneficial in deficient or heavily-training men.2627
Quality standards
Zinc bisglycinate chelate, verified identity and potency.
Research callout
Athletes lose zinc through sweat — repletion matters most under high training load.
Reviewed by the 4 Gauge research team
