By Jeremiah Velasquez, FNP-BC, AGACNP-BC
Founder, Steel City HRT & Weight Loss | Board-Certified Family & Acute Care Nurse Practitioner
NPI: 1841894003

The relationship between IGF-1 and testosterone in body composition is sequential, not simultaneous. Testosterone must be optimized first to prime androgen receptors and prepare skeletal muscle tissue for IGF-1's anabolic signal. Men who introduce IGF-1-stimulating peptides without an established hormonal baseline typically experience water retention rather than lean mass accrual.

You've probably been told that adding IGF-1 peptides to your protocol is the fastest path to the body composition you're after. You might have even tried it. And if those results left you with more water weight than lean muscle — more frustration than progress — that's not a peptide problem. That's a sequencing problem.

In mathematics, the order of operations isn't a suggestion. Get it wrong and the equation collapses. The same principle applies to hormone optimization. IGF-1 and testosterone are two of the most powerful anabolic signals in the human body, but they don't operate on a level playing field. One has to come first — and getting that wrong is one of the most expensive and most avoidable mistakes in men's performance medicine.

I'm Jeremiah Velasquez, FNP-BC, AGACNP-BC, founder of Steel City HRT & Weight Loss. In my clinical experience, peptide chasing without a hormonal foundation is one of the most common reasons men plateau — and one of the most fixable. Let's break down why the order matters, and what getting it right actually looks like.

Why Aren't Peptides Producing the Lean Mass You Were Expecting?

You're not imagining it. You did the research, sourced what you could find, followed the protocol outlined in a forum or thread — and the results still don't match what you were promised. That's not a failure of discipline. That's a failure of sequencing.

Testosterone is a steroid hormone produced primarily in the Leydig cells of the testes. It is the primary anabolic hormone in the male body, governing skeletal muscle protein synthesis, androgen receptor density, satellite cell activation, and the downstream uptake of anabolic signals — including IGF-1.

Here's the problem. When testosterone is suboptimal — even if it falls within a "normal" reference range — the cellular machinery that IGF-1 depends on is operating at a deficit. The androgen receptors that IGF-1 needs in muscle tissue are underrepresented. The satellite cells that should respond to IGF-1's signal are partially dormant. The result is predictable.

There are three physiological realities that make a peptides-first approach a losing strategy:

One. Androgen receptor density in skeletal muscle is testosterone-dependent. Without adequate testosterone, there are fewer receptors for IGF-1 to target — and a diminished signal is a diminished outcome.

Two. Satellite cell activation — the mechanism behind true muscle hyperplasia, or new muscle cell creation — is initiated by testosterone. IGF-1 amplifies a process that testosterone starts. Reverse the order and you're amplifying a process that hasn't started yet.

Three. IGF-1 promotes sodium retention at the renal level. In a low-testosterone environment, where anabolic offset is blunted, that fluid retention becomes the dominant effect — not lean mass accrual.

Key takeaway: Suboptimal testosterone reduces androgen receptor density and satellite cell activity, leaving IGF-1 with fewer anabolic targets — and making water retention the dominant outcome rather than lean mass.

How Does Testosterone Prepare the Body for IGF-1 to Work?

Here's what most people don't know. IGF-1 and testosterone don't operate independently. They share a mechanistic relationship that is hierarchical — and testosterone holds the senior position.

Think of testosterone as the electrical grid and IGF-1 as the high-performance appliances. You can own every piece of equipment on the market, but without the grid running at full capacity, none of it operates at spec.

Mechanistically: testosterone binds to androgen receptors (AR) in skeletal muscle cells, activating the PI3K/Akt/mTOR pathway — the central signaling cascade for muscle protein synthesis. Simultaneously, testosterone upregulates IGF-1 receptor expression in muscle tissue and activates satellite cells, the muscle stem cells responsible for true hyperplasia rather than simple hypertrophy. According to research published in the Journal of Clinical Endocrinology and Metabolism, testosterone directly stimulates IGF-1 receptor density in skeletal muscle — meaning the same circulating IGF-1 level produces a quantifiably stronger anabolic response in a testosterone-replete environment compared to a testosterone-deficient one.

IGF-1 itself — or Insulin-Like Growth Factor 1, a peptide hormone produced primarily by the liver in response to growth hormone stimulation — drives both hypertrophy (enlargement of existing muscle cells) and hyperplasia (creation of new muscle cells via satellite cell differentiation). Hyperplasia is the superior body composition outcome. It's also the one that requires a testosterone-primed environment to occur at meaningful scale.

I've been on both sides of this equation — as a patient chasing peptide results before my own hormonal baseline was established, and as a provider watching that pattern repeat in men who deserved better clinical guidance. The difference in outcomes when the sequencing is corrected is not subtle.

Key takeaway: According to the Journal of Clinical Endocrinology and Metabolism, testosterone upregulates IGF-1 receptor density in skeletal muscle, meaning an optimized testosterone environment produces measurably stronger anabolic outcomes from the same IGF-1 level.

What Does the Correct Hormonal Sequencing Actually Look Like?

Effective body recomposition through the testosterone-IGF-1 axis follows a structured timeline — not a simultaneous compound stack.

Starting with a comprehensive hormonal baseline evaluation: total and free testosterone, SHBG, estradiol, IGF-1, and a metabolic panel. Followed by testosterone optimization through a testosterone replacement therapy protocol targeting functional ranges — not "normal" reference values, but the 700–1,000 ng/dL range associated with clinical optimization, consistent with Endocrine Society clinical practice guidelines. Ending with an 8–12 week reassessment to confirm the hormonal environment is established before a growth hormone secretagogue protocol is introduced.

Most men spend three to six months on TRT before peptides belong in the conversation. That isn't a delay — it's foundation work. And it's the difference between a protocol that produces water weight and one that produces body recomposition.

Secondly, sourcing matters more than most men realize. The peptide market is saturated with research-use-only (RUO) compounds — substances manufactured for laboratory applications, never for human administration. Purity, sterility, and potency claims on RUO products are unverified by any regulatory standard. That's not a technicality. The consequences range from ineffectiveness to real injection-site and systemic risk. A compound that was never made for your bloodstream doesn't belong in it.

You've got two options. Continue adding compounds to a suboptimal hormonal environment and wonder why the results don't match the theory — or build the foundation correctly and let IGF-1 work in the environment it was designed for.

Key takeaway: The Endocrine Society recommends targeting testosterone levels of 700–1,000 ng/dL for optimization; establishing this baseline before introducing GH secretagogues consistently produces superior body composition outcomes compared to adding peptides to a hormone-deficient environment.

Why Are Men Across the Country Choosing Steel City HRT & Weight Loss for Hormone Optimization?

Steel City HRT & Weight Loss is LegitScript-certified — the same certification required of legitimate online pharmacies — which means our sourcing standards, prescribing practices, and patient protocols meet independently verified benchmarks. Every peptide and hormone we prescribe is sourced exclusively from 503a compounding pharmacies operating under USP 797 sterility requirements. We love a good neighborhood BBQ, but we recommend keeping the DIY projects limited to the patio — not your bloodstream.

Our model is fully telehealth. No clinic visit required. Starting with comprehensive labs, followed by a provider-led telehealth consult, and ending with individualized treatment delivered to your door. We don't just write the script and send you on your way — we stay in your corner throughout the optimization process through our HIPAA-secure app, adjusting protocols based on how your labs and your body respond.

Programs include testosterone replacement therapy, peptide therapy, GLP-1 metabolic optimization, and low-dose naltrexone — each sequenced deliberately, not stacked impulsively.

Ready to Build the Foundation and Actually See Results?

The system made this harder than it needed to be. Steel City removes every unnecessary barrier: no waiting rooms, no unanswered questions, no guessing about what your levels are or what to do about them.

If you've been chasing results with compounds that haven't been given a proper environment to work — this is where that changes. Two options. Keep adding to a broken stack and wonder why the results don't match the theory, or start at the beginning, get your labs, and build a protocol that respects your body's actual biochemistry.

Labs, consult, optimization — that easy.

It all starts at steelcity-trt.com.

Frequently Asked Questions

Q: What is IGF-1 and how does it relate to muscle growth? A: IGF-1, or Insulin-Like Growth Factor 1, is a hormone produced by the liver in response to growth hormone stimulation. It drives both muscle hypertrophy, or enlargement of existing cells, and hyperplasia, the creation of new muscle cells through satellite cell differentiation. IGF-1's anabolic effect on skeletal muscle is significantly amplified when testosterone levels are optimized.

Q: Does testosterone increase IGF-1 levels? A: Testosterone supports IGF-1 receptor expression in skeletal muscle and stimulates hepatic IGF-1 production. According to the Journal of Clinical Endocrinology and Metabolism, testosterone-replete men exhibit stronger anabolic responses to equivalent IGF-1 levels compared to testosterone-deficient men, making hormonal baseline establishment a prerequisite for effective peptide therapy outcomes.

Q: Why do IGF-1 peptides cause water retention without testosterone optimization? A: IGF-1 promotes sodium retention at the kidney level. When testosterone is suboptimal, androgen receptor density and satellite cell activity are reduced, which blunts IGF-1's anabolic potential. Without the muscle-building payoff, water retention becomes the dominant effect. Testosterone optimization restores the cellular environment needed for IGF-1 to produce lean mass instead of fluid accumulation.

Q: What peptides are used to raise IGF-1 levels? A: Growth hormone secretagogues such as CJC-1295, Ipamorelin, and Sermorelin are studied clinically for their ability to stimulate pituitary GH release, which prompts the liver to produce IGF-1. These peptides are most effective when introduced within a structured hormonal optimization protocol that begins with testosterone assessment and baseline establishment.

Q: Are RUO peptides safe for human use? A: Research-use-only (RUO) peptides are not manufactured to human-use safety standards and are not subject to the sterility, potency, or purity verification requirements that govern 503a compounding pharmacies under USP 797. RUO products carry unverifiable purity claims and real risks including contamination, improper dosing, and sterility failures. Clinically prescribed peptides from a LegitScript-certified provider sourcing exclusively from 503a pharmacies meet verified safety standards and are prescribed under clinical supervision.

Q: How long should I be on testosterone therapy before adding peptide therapy? A: Most clinicians recommend a minimum of 8–12 weeks on an established testosterone replacement protocol before introducing growth hormone secretagogues. This window allows testosterone levels to stabilize, androgen receptor density to normalize, and satellite cell activity to recover — creating the hormonal environment in which IGF-1 produces clean anabolic results. Individual timelines depend on baseline labs and clinical response.

This content is for informational purposes only and does not constitute medical advice. Consult a licensed provider before beginning any hormone or weight loss therapy. Jeremiah Velasquez, FNP-BC, AGACNP-BC, is a licensed nurse practitioner. Steel City HRT & Weight Loss is a LegitScript-certified telehealth clinic.