What Are Peptides and How Do They Work?

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Article: What Are Peptides and How Do They Work?  |  Category: Peptide Therapy  |  Authored by: Brian Lamkin, DO

What Peptides Are

Peptides are short chains of amino acids linked by peptide bonds. They are distinguished from proteins by their size: peptides typically contain 2 to 50 amino acids, while proteins contain 50 or more^[1]. The human body produces over 7,000 naturally occurring peptides that regulate virtually every physiological process: growth hormone secretion, tissue repair, immune surveillance, neurotransmission, pain modulation, appetite regulation, sleep architecture, and cellular energy production. Insulin is a peptide. Oxytocin is a peptide. Growth hormone releasing hormone (GHRH) is a peptide. The body's signaling network is built on peptide communication. Therapeutic peptides are synthetic versions of these natural signaling molecules, designed to supplement or enhance specific signaling pathways that have declined with aging, disease, or environmental stress.

How Peptides Differ from Drugs

Most pharmaceutical drugs work by blocking, inhibiting, or overriding a biological process. Beta-blockers block adrenergic receptors. PPIs block the proton pump. Statins inhibit HMG-CoA reductase. NSAIDs block cyclooxygenase. The drug forces a change in the system. Peptides work differently. They signal cells to activate a process the body already has the machinery to perform. A growth hormone secretagogue peptide does not inject growth hormone into the body. It signals the pituitary gland to produce and release more of its own growth hormone. BPC-157 does not directly rebuild tissue. It activates the angiogenic (blood vessel forming) and tissue repair pathways that the body uses for healing. This "instruct rather than override" mechanism is why peptides generally produce fewer side effects than drugs: they work within the body's existing regulatory framework, amplifying a natural process rather than forcing an artificial one.

Growth Hormone Secretagogues

Growth hormone (GH) secretion declines approximately 14 percent per decade after age 30. By age 60, most adults produce 75 percent less GH than they did at age 25. This decline contributes to muscle loss, increased visceral fat, reduced bone density, impaired recovery, cognitive decline, and accelerated aging. Growth hormone secretagogue peptides stimulate the pituitary to produce its own GH in physiological pulses^[2]. CJC-1295 is a synthetic analog of GHRH that extends the half-life of the natural hormone, producing sustained GH stimulation. Ipamorelin is a selective growth hormone releasing peptide (GHRP) that stimulates GH release through the ghrelin receptor without significant effects on cortisol or prolactin. The CJC-1295/ipamorelin combination is the most commonly prescribed GH secretagogue protocol, administered as a subcutaneous injection at bedtime (to augment the natural nocturnal GH pulse). Response is monitored through IGF-1 levels, which reflect integrated GH activity over the preceding weeks.

Tissue Repair Peptides

BPC-157 (Body Protection Compound-157) is a 15-amino-acid peptide derived from human gastric juice that has demonstrated remarkable tissue repair properties across multiple tissue types^[3]. BPC-157 promotes angiogenesis (new blood vessel formation at the repair site), upregulates growth factor expression, accelerates tendon and ligament healing, promotes muscle repair, protects and heals the gastrointestinal mucosa, and has demonstrated neuroprotective properties. It is used clinically for tendon injuries, joint repair, post-surgical healing, gut barrier restoration, and musculoskeletal recovery. Administration: subcutaneous injection (systemic effect) or oral capsule (GI-specific effect for gut healing). TB-500 (Thymosin Beta-4) is a complementary tissue repair peptide that promotes tissue regeneration through different mechanisms (actin regulation, anti-inflammatory effects, stem cell differentiation). The BPC-157/TB-500 combination is frequently used for complex musculoskeletal injuries and post-surgical recovery.

Immune Modulating Peptides

Thymosin alpha-1 is a 28-amino-acid peptide naturally produced by the thymus gland that modulates immune function through dendritic cell maturation, T-cell activation, and natural killer cell enhancement. The thymus involutes (shrinks) with age, reducing thymosin production and contributing to immunosenescence (age-related immune decline). Synthetic thymosin alpha-1 is used clinically for immune support in chronic infections (hepatitis B, hepatitis C), immune deficiency states, and as an adjunct in cancer immunotherapy. In functional medicine, thymosin alpha-1 is used for patients with recurrent infections, poor vaccine response, or documented immune underfunction. It is administered as a subcutaneous injection, typically 2 to 3 times per week.

Metabolic and Body Composition Peptides

Tesamorelin is an FDA-approved GHRH analog that specifically targets visceral fat reduction. It stimulates GH secretion and has been shown to reduce visceral adipose tissue by 15 to 20 percent in clinical trials. Unlike direct GH administration, tesamorelin maintains the pulsatile GH secretion pattern and the negative feedback regulation that prevents excessive GH levels. AOD-9604 is a modified fragment of human growth hormone (amino acids 177 to 191) that promotes fat metabolism without the growth-promoting effects of full-length GH. It stimulates lipolysis (fat breakdown) and inhibits lipogenesis (fat formation) without affecting blood glucose or IGF-1 levels. These metabolic peptides are used alongside dietary structure, exercise, and metabolic optimization (addressing insulin resistance, thyroid function, and cortisol balance) for patients whose body composition does not respond adequately to lifestyle intervention alone.

Cognitive and Neuroprotective Peptides

Semax is a synthetic analog of the naturally occurring peptide ACTH(4-10) that has demonstrated neuroprotective and cognitive-enhancing properties. It increases brain-derived neurotrophic factor (BDNF) expression, promotes neuroplasticity, and has been used clinically for cognitive impairment, stroke recovery, and neurodegenerative conditions. Selank is a synthetic analog of the naturally occurring immunomodulatory peptide tuftsin with anxiolytic (anxiety-reducing) and nootropic (cognitive-enhancing) properties. Both are administered as nasal sprays, providing direct delivery to the central nervous system through the olfactory pathway. These peptides are used in functional medicine for patients with cognitive decline, brain fog, anxiety, and neurodegenerative concerns, particularly when neuroinflammation and BDNF depletion are identified as contributing factors.

Why Peptide Source and Quality Matter

The most important safety consideration in peptide therapy is not the peptide itself but its source. Peptides obtained from unregulated online suppliers, "research chemical" companies, or overseas sources without pharmaceutical oversight may contain impurities (endotoxins, heavy metals, degradation products), incorrect concentrations, mislabeled compounds, or non-sterile preparations. At The Lamkin Clinic, all peptides are prescribed by a licensed physician and obtained exclusively from companies that conduct potency and purity testing, and provide certificates of analysis. This is not optional. It is a fundamental safety requirement. Peptides are prescription medications and should be treated as such.

How Peptides Fit Into Functional Medicine

Peptide therapy is not a standalone intervention. It is one layer in a comprehensive functional medicine treatment plan that addresses the root causes of decline while using peptides to enhance specific physiological processes. The foundation must be in place first: metabolic optimization (fasting insulin normalization, body composition improvement), hormonal balance (thyroid, testosterone, DHEA-S, cortisol), gut health restoration (dysbiosis treatment, barrier repair), inflammation reduction (hs-CRP optimization, omega-3 balance), sleep optimization, and exercise programming. Peptides amplify the results of this foundation. A GH secretagogue peptide produces significantly better results when insulin sensitivity, sleep quality, and exercise programming are optimized than when prescribed in isolation to an insulin-resistant, sleep-deprived, sedentary patient. The peptide is the accelerant. The foundation is the fuel.

Who Is a Candidate for Peptide Therapy

Peptide therapy candidates are patients who have optimized the foundational elements (nutrition, exercise, sleep, stress management, hormone optimization) and either plateaued in their progress or have specific clinical needs that peptide signaling can address: declining GH axis function confirmed by low IGF-1, persistent tissue injury or slow healing, immune underfunction with recurrent infections, body composition that does not respond to metabolic intervention, or cognitive decline with documented neuroinflammation. Peptide therapy is not appropriate as a first-line intervention for patients who have not addressed diet, sleep, exercise, and metabolic health. It is not a shortcut. It is a precision tool for patients who have built the foundation and need targeted enhancement of specific physiological pathways.

The Lamkin Clinic Approach to Peptide Therapy

At The Lamkin Clinic, peptide therapy is prescribed within a comprehensive evaluation framework. Baseline assessment includes IGF-1 (GH axis status), DHEA-S (adrenal and neurosteroid reserve), fasting insulin and HOMA-IR (metabolic status), hs-CRP (inflammatory status), full thyroid panel, sex hormone panel, body composition analysis (DEXA), and condition-specific assessments based on the clinical indication. Peptide selection is based on the identified deficiency or clinical need, not patient request or trend-driven prescribing. Monitoring includes follow-up IGF-1 (for GH secretagogues), symptom tracking, body composition reassessment, and safety labs at defined intervals. The goal is measurable improvement in the specific physiological target, confirmed by objective data, with the minimum effective intervention.

The Lamkin Clinic, Edmond Oklahoma | lamkinclinic.com

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References and Further Reading

1. [1]Fosgerau K, Hoffmann T. Peptide therapeutics: current status and future directions. Drug Discov Today. 2015;20(1):122-128.
2. [2]Ghigo E, et al. Growth hormone-releasing peptides. Eur J Endocrinol. 1999;141(5):445-460.
3. [3]Sikiric P, et al. Brain-gut axis and pentadecapeptide BPC 157: theoretical and practical implications. Curr Neuropharmacol. 2016;14(8):857-865.