A peptide is a short chain of amino acids — the building blocks of proteins — linked together by peptide bonds. While proteins can consist of hundreds or thousands of amino acids, peptides are typically defined as chains of 2–50 amino acids. This structural simplicity belies their extraordinary functional complexity.
Peptides as Biological Messengers
The human body uses peptides as signaling molecules throughout virtually every physiological system. Hormones, neurotransmitters, immune modulators, and growth factors are all peptides or peptide-derived compounds. Insulin (51 amino acids), glucagon, oxytocin, vasopressin, and growth hormone-releasing hormone are all endogenous peptides.
What makes therapeutic peptides particularly compelling is their mechanism: rather than replacing a hormone or blocking a receptor, most therapeutic peptides work by signaling your body's own systems to upregulate a function. Sermorelin doesn't deliver growth hormone — it signals your pituitary to produce more of its own. BPC-157 doesn't patch tissue directly — it activates growth factor signaling cascades that drive native repair mechanisms.
Categories of Therapeutic Peptides
Growth hormone secretagogues — peptides that stimulate growth hormone production: Sermorelin, CJC-1295, Ipamorelin. Used for body composition, recovery, sleep quality, and anti-aging applications.
Tissue repair peptides — BPC-157, Thymosin Beta-4. Used for injury recovery, gut health, and systemic inflammation reduction.
Metabolic peptides — GLP-1 agonists (semaglutide, tirzepatide), AOD-9604. Used for weight management and cardiovascular risk reduction.
The Stability Challenge
The primary limitation of peptides as therapeutics has historically been stability. Peptides are rapidly degraded by enzymes in the gut and bloodstream, making oral delivery largely ineffective. This is why most therapeutic peptides are administered subcutaneously — routes that allow direct entry into the bloodstream before enzymatic degradation occurs.
Regulatory Landscape
The regulatory status of therapeutic peptides varies. Some are FDA-approved pharmaceuticals (semaglutide, sermorelin). Others are available through compounding pharmacies. The landscape has evolved significantly following FDA guidance in 2023–2024, making physician oversight essential for anyone pursuing peptide therapy.