MOTS-c

Oxytocin is a 9-amino-acid hormone made in the hypothalamus, famous as the chemistry behind labor contractions, breastfeeding, and social bonding. As an injectable drug it is FDA-approved to induce labor and control postpartum bleeding, but the intranasal 'love hormone' versions sold for trust, anxiety, and autism are experimental and the human results are genuinely mixed. The hype runs well ahead of the evidence.

Rusfertide (brand name Mimrylo) is an injectable peptide that mimics hepcidin, the body's master hormone for controlling iron, and it is used to manage polycythemia vera (PV), a blood cancer that makes too many red blood cells. By limiting iron availability, it throttles red blood cell production and reduces the need for repeated blood draws (phlebotomy). It is not a research-only or gray-market peptide: the FDA approved it on August 28, 2026 for adults with PV, after a positive phase 3 trial.

Cetrorelix is a GnRH antagonist: a modified 10-amino-acid version of the brain's gonadotropin-releasing hormone that blocks its receptor instead of activating it. Sold as Cetrotide and FDA-approved since August 2000, its job in IVF is narrow and important: it stops the body's own LH surge from releasing eggs too early while the ovaries are being stimulated. It is a well-established fertility drug with decades of use, and it is not a tool for anything else people sometimes imagine it for.

HCG is a hormone produced in pregnancy that happens to be an almost perfect mimic of luteinizing hormone. That single fact is why it has two completely unrelated uses: it is an approved fertility medicine, and it is the standard tool for keeping the testicles working during testosterone therapy. It is also the basis of the discredited HCG diet, which is a separate story and not supported by evidence.

Kisspeptin is the master switch that tells your brain to start reproduction. It is a family of peptides (the full length is kisspeptin-54, with shorter active fragments KP-14, KP-13, and KP-10) made from the KISS1 gene, and it acts as the upstream trigger for the entire reproductive hormone cascade. It is not an approved drug, but it has been tested in real human trials for fertility, hypothalamic amenorrhea, and male hypogonadism, with promising early results.

Gonadorelin is a synthetic copy of natural GnRH (gonadotropin-releasing hormone), a 10-amino-acid peptide (pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2) that tells the pituitary to release LH and FSH. It was once FDA-approved (Factrel) for testing pituitary function, but that brand is discontinued and no approved gonadorelin product is marketed in the US today. In the peptide world it is mostly used off-label to keep the testes working during testosterone replacement, and the catch is that timing matters enormously: pulse it and you stimulate, give it continuously and you shut the system down.