Want to build muscle? Stop obsessing over testosterone

In almost every corner of the fitness industry, testosterone dominates the conversation on muscle growth. Supplements, sleep hacks, and lifestyle protocols promise to "optimize" testosterone, and many people believe it's the single most important variable in hypertrophy. But the truth is more nuanced.

Muscle growth is governed by a tightly regulated, interdependent web of anabolic hormones—testosterone, growth hormone (GH)/IGF-1, and insulin. Of these, testosterone may be the most popular, but it's arguably the least controllable for natural athletes. Meanwhile, insulin—the most responsive, manipulable, and anabolic hormone of the three—remains underappreciated in most training circles.

This post will break down the real physiology of muscle growth, what’s actually achievable naturally, and why most people are focusing on the wrong levers.

The Three Hormonal Pillars of Muscle Growth

To understand muscle anabolism, we need to start by examining the three major hormonal drivers:

Testosterone – the archetypal male hormone, linked to strength, aggression, and size
Growth Hormone (GH)/IGF-1 – a regulatory axis involved in cellular repair, recovery, and tissue remodeling
Insulin – often misunderstood as a "fat storage hormone," but arguably the most actionable anabolic tool for naturals

Let’s explore each one in context.

Testosterone: Overrated and Difficult to Control

Testosterone is vital for muscle protein synthesis, strength, and libido. It increases nitrogen retention, enhances recovery, and supports a favorable environment for hypertrophy. However, increasing testosterone naturally is extremely difficult and the returns are often overestimated.

What's Achievable Naturally?

Sleep, nutrition, and resistance training can help restore low testosterone to baseline, but rarely push it beyond physiological norms.
Lifestyle interventions (improved sleep hygiene, lower body fat, stress reduction) may raise testosterone by 10–20%, typically bringing deficient levels back into the normal range—not into supraphysiological territory.
Supplements like ashwagandha, tongkat ali, D-aspartic acid, and zinc can offer minor increases in total testosterone, often 5–10% at best—and many studies show no consistent effect.

The SHBG Factor

Even if total testosterone goes up, your free testosterone—the biologically active portion—depends on Sex Hormone-Binding Globulin (SHBG). This protein binds to testosterone, rendering it inactive.

Raising total testosterone is not sufficient if SHBG increases in parallel.
High-protein diets, caloric restriction, and endurance training can increase SHBG.
Free testosterone is a function of both total testosterone and SHBG—and most blood panels miss this nuance.

Without a corresponding drop in SHBG, total testosterone increases are often cosmetic rather than functional.

Enhanced Bodybuilders: A Useful (if Extreme) Case Study

Among amateur enhanced lifters, testosterone (via injections or oral derivatives) is often the first pharmacological step. But in the IFBB Pro circuit, testosterone is just one part of a complex anabolic protocol. More advanced users prioritize insulin and growth hormone to drive extreme muscle gain.

This distinction is important—not because we advocate exogenous use—but because it highlights where the ceiling lies. Testosterone delivers early returns, but it plateaus. Beyond that, it’s nutrient partitioning, recovery dynamics, and synergy with other hormones (notably insulin) that determine continued growth.

Growth Hormone and IGF-1: Marginal Gains for Naturals

Growth hormone (GH) is secreted in pulses—primarily at night and during intense training. Its downstream metabolite, Insulin-like Growth Factor 1 (IGF-1), is the main driver of GH’s anabolic effects.

Natural GH secretion can be enhanced by:

Deep sleep (especially slow-wave stages)
Fasting
High-intensity interval training or resistance training

But the caveat is this:

Exercise and sleep do raise GH, but they do not significantly raise IGF-1 area under the curve (AUC).
The spike in GH is transient—typically lasting 30–90 minutes—and does not accumulate in a way that materially increases long-term IGF-1 exposure.
IGF-1 is heavily regulated by liver function, nutrient availability, and systemic inflammation. You can’t will it to rise meaningfully without pharmacological GH.

For this reason, while GH/IGF-1 is necessary, it’s not a practical lever for natural lifters.

Insulin: The Most Overlooked Natural Anabolic Hormone

Insulin is arguably the most underappreciated and controllable anabolic hormone in the muscle-building toolkit.

Contrary to popular belief, insulin doesn’t just shuttle glucose into fat cells. In fact, it is anti-catabolic in muscle tissue and synergistic with amino acids and resistance training.

Mechanisms of Action

Inhibits muscle protein breakdown
Promotes amino acid uptake into muscle cells
Enhances glycogen synthesis, boosting training volume and muscle fullness
Supports the activation of mTOR, the key pathway for hypertrophy

The Real Leverage

Here’s what makes insulin so potent:

While testosterone levels might increase by 10–20%, insulin levels can be increased by 10–20x (or more) after a single meal.
A fasting insulin of 3–5 μU/mL can spike to 50–150 μU/mL following a high-carbohydrate meal with protein—a 1,000–3,000% increase.
This response is natural, legal, and diet-controlled.

More importantly, insulin is not anabolic on its own—but in the presence of amino acids (especially leucine), it becomes a co-activator of muscle growth. This makes nutrient timing critical.

Optimizing Insulin for Hypertrophy

Post-workout window: carbs + protein (e.g., whey + rice) enhances insulin secretion and replenishes glycogen.
Pre-workout insulin sensitivity: maintaining low body fat, high sleep quality, and aerobic fitness enhances your insulin response.
Intra-workout carbs (like cyclic dextrin or glucose) can further boost insulin during training, fueling volume and recovery.

Unlike testosterone or GH, insulin is something you can manipulate meal by meal, making it the most practical anabolic hormone available to natural athletes.

Final Thoughts: Shift Your Focus to What You Can Control

Most natural lifters spend years chasing minor testosterone increases through lifestyle tweaks and overpriced supplements. But testosterone is tightly regulated. And GH/IGF-1, though compelling in theory, is limited in what you can achieve without pharmaceuticals.

Insulin, however, is fully within your control—and incredibly potent when paired with intelligent training and nutrition.

If you want to build muscle efficiently, stop fixating on the hormone you wish you could boost. Focus instead on the one you can—insulin—and build your strategy around maximizing its effect.

The strongest physiques are not built through marginal testosterone hacks. They’re built through metabolic precision, nutrient timing, and consistent training—all underpinned by the smart use of insulin dynamics.

Understand your levers. Use them well. The results will follow.