A receptor without a ligand, and the stomach hormone that turned out to fill it

Published 26 October 2026 · REVIVE LAB UAE Research Desk · 5 min read
Kojima, Kangawa and colleagues reported in Nature in 1999 the purification of a 28-residue peptide from rat stomach that activated the orphan growth hormone secretagogue receptor and released growth hormone from pituitary cells. They named it ghrelin and showed it carried an unusual octanoyl group on its third residue, serine, required for activity. The finding closed a loop opened by synthetic secretagogues developed in the 1980s and added a stomach-to-pituitary signal to the axis.

The orphan receptor

Synthetic peptides and small molecules that released growth hormone by a route distinct from the releasing hormone had been known since the late 1970s, and their receptor was cloned in 1996. It was an orphan: a receptor with no identified natural ligand. Reverse pharmacology — using the receptor to hunt for its ligand in tissue extracts — found it in the stomach rather than the brain.

The receptor is expressed in the pituitary and hypothalamus, which is where the secretagogues act.

What ghrelin is

A 28-residue peptide with an eight-carbon fatty acid attached to serine 3 by a specific enzyme, ghrelin O-acyltransferase, identified in 2008. Without the acyl group it does not bind the receptor. It rises before meals and falls after, and besides releasing growth hormone it stimulates appetite, which became its better-known role.

It is the only known peptide hormone with this kind of fatty-acid modification.

Where it sits

Alongside the releasing hormone and somatostatin as a third regulator of secretion, amplifying pulses rather than initiating them. Synthetic agonists of its receptor are the growth hormone secretagogue class, including macimorelin, approved in 2017 as a diagnostic agent. None of this describes any use of the material in this pack.

Somatropin is supplied by REVIVE LAB UAE for laboratory research use only, with identity and purity documented for the batch. It is not for human or veterinary use, and no dosing, administration or protocol guidance is provided.

What it costs

FormatStrengthPriceAvailability
HGH Somatropin Pack24 mg (72 IU)AED 850In stock

Delivery is AED 40 flat and free on orders over AED 700. Payment is cash on delivery anywhere in the UAE, or USDT (TRC20) in advance, which takes 5% off the order total.

Frequently asked

The orphan receptor?

Synthetic peptides and small molecules that released growth hormone by a route distinct from the releasing hormone had been known since the late 1970s, and their receptor was cloned in 1996. It was an orphan: a receptor with no identified natural ligand. Reverse pharmacology — using the receptor to hunt for its ligand in tissue extracts — found it in the stomach rather than the brain.

Does REVIVE LAB UAE provide dosing guidance?

No. REVIVE LAB UAE supplies research materials and provides no dosing, administration or protocol guidance of any kind. Every product is sold for laboratory research use only and is not for human or veterinary consumption.

How fast is delivery in the UAE?

Stock is held in Dubai. An order confirmed before 4 PM Dubai time is dispatched the same working day, reaching Dubai and Abu Dhabi the same day and the remaining emirates within 24 hours. Delivery is AED 40 flat and free over AED 700.

HGH Somatropin Pack — in stock, dispatched from Dubai
HPLC-verified, lot certificate on every carton, 24-hour delivery nationwide. Browse the catalogue → All peptides UAE

Related reading

Supplied for laboratory research use only. Not for human or veterinary consumption. REVIVE LAB UAE provides no dosing, administration or protocol guidance.