# Ipamorelin: Bone Growth, GH Selectivity, and the Cited Record > Ipamorelin lengthened rat bone at 18-450 microg/day and raised bone mineral content without raising cortisol. A research digest, bone-skeletal evidence first. A selective growth hormone secretagogue, read from the published literature. Bone-skeletal data first. Every number sourced. Nothing sold here. ## TL;DR Ipamorelin is a lab-made peptide (a short chain of five amino acids). It tells the pituitary gland — a pea-sized gland under the brain — to release a pulse of growth hormone. Its trick is being clean: it raises growth hormone without raising the stress hormone cortisol or the hormone prolactin. That clean profile is the whole reason researchers cared about it. The data that leads this site is bone. In rats, ipamorelin made leg bones grow longer, and it raised the amount of mineral packed into bone. It also helped rebuild bone that steroids had broken down. All of that is animal work. In people, the record is thin. One human trial tested it after bowel surgery. It did not beat placebo. It was never approved as a medicine anywhere. What people report from research use — the sleep, the flushing, the hunger, the downsides — sits on the [Ipamorelin effects](/effects) page, clearly labeled as anecdote, not proof. ## What the bone studies measured Bone is where ipamorelin's preclinical record is strongest. Subcutaneous ipamorelin at 18, 90, and 450 microg/day (split three times daily, 15 days) raised the longitudinal bone growth rate of adult female rats from 42 microm/day on vehicle to 44, 50, and 52 microm/day — a clean dose-response, with no change in total IGF-1, IGF binding proteins, or bone turnover markers [1]. (Longitudinal bone growth = lengthening at the growth plate. IGF-1 = insulin-like growth factor 1, a hormone that carries many of growth hormone's downstream effects.) Mineral content moved too. Ipamorelin 0.5 mg/kg/day, delivered continuously by an implanted osmotic minipump for 12 weeks, raised total tibial and vertebral bone mineral content (measured by DXA scan) in adult female rats versus vehicle. Cortical volumetric bone density did not change [2]. The reading: bigger bone dimensions, not denser bone. Steroids break bone down. Ipamorelin pushed back. At 100 microg/kg three times daily for 3 months, alongside a glucocorticoid steroid, it raised the periosteal bone formation rate roughly four-fold versus steroid alone and lifted maximum tetanic muscle tension [3]. The bone-skeletal lens is the spine of this digest. The full picture is on the [ipamorelin benefits](/benefits) page. ## The selectivity that defines it Ipamorelin's founding paper named it the first selective growth hormone secretagogue. In rat pituitary cells, anaesthetised rats, and conscious pigs, it released growth hormone potently — pig ED50 of 2.3 nmol/kg, against 3.9 nmol/kg for the older peptide GHRP-6 — yet did not raise ACTH or cortisol above the level seen with GHRH, even at doses more than 200-fold over its growth-hormone ED50 [4]. (ED50 = the dose that produces half the maximum effect. ACTH = the pituitary signal that drives cortisol, the body's main stress hormone.) That is the headline. Older growth-hormone-releasing peptides dragged cortisol and prolactin up with the growth hormone. Ipamorelin left them flat. The mechanism is a single receptor: GHS-R1a, the ghrelin receptor, on the pituitary's GH-producing cells. Ghrelin is the body's hunger hormone; ipamorelin mimics it at that receptor. ## What humans actually got Human evidence is short and, for the indication tested, negative. The only published Phase 2 trial gave 0.03 mg/kg intravenously twice daily for up to 7 days to 114 adults after bowel surgery. It missed its primary endpoint: median time to first tolerated meal was 25.3 hours with ipamorelin versus 32.6 hours with placebo (p=0.15) [5]. No further trials followed. One human pharmacokinetic study mapped the basics: a terminal half-life of about 2 hours, a single growth-hormone pulse peaking near 40 minutes after dosing [6]. (Half-life = the time for blood levels to fall by half.) That is the human file. No approval. No Phase 3. The doses studied — in every species — are on the [Ipamorelin research](/research) page, third person, never as instruction. ## What this site is A digest. It reads the published ipamorelin literature and reports what was measured — dose, species, route, outcome — with every number tied to a citation. The word "store" in the domain is a name, not a counter. Nothing here is for sale. No vendor. No clinic. No prescription. For the reported effects and the cited cautions, see [Ipamorelin effects](/effects). For the source list, see [Ipamorelin references](/references). --- A terminal read of the ipamorelin literature: bone data logged where the studies confirm it, the lone failed human trial left in plain view, no clinic behind the console and nothing here dosed or sold.