Ghrelin

Where it comes from

Made in

Endocrine cells in the lining of the stomach, mostly the fundus, with less from the small intestine and pancreas

Sent out by

Fasting: levels climb before an expected meal and fall within an hour of eating

Acts on

• Hypothalamus (NPY and AgRP neurons)
• Pituitary
• Vagus nerve
• Pancreas

What it does

• Signals hunger and starts meals
• Releases growth hormone from the pituitary ¹
• Favours fat storage and raises blood glucose

In medicine

• Macimorelin, an oral ghrelin receptor agonist, is approved to diagnose growth hormone deficiency in adults
• Anamorelin is approved in Japan for the weight loss of cancer
• Ghrelin falls in the months after gastric bypass in many studies, though not all; how much it explains the loss of appetite is debated

Beyond the body’s own use

• The “growth hormone secretagogues” ipamorelin, GHRP-2, GHRP-6 and hexarelin, and the oral MK-677 (ibutamoren), all imitate ghrelin at its receptor, and none is an approved medicine. In 65 healthy older adults given MK-677 for a year, fat-free mass rose by about a kilogram, but fasting glucose rose too and insulin sensitivity fell ²
• Peptides of this family obtained outside the approved supply are not reviewed for safety, effectiveness or quality, and the whole class is banned in sport at all times ⁴
• Anamorelin was refused in Europe in 2017: the regulator found the gain in lean mass small and no improvement in grip strength or in how patients felt ³
• Ghrelin itself has been infused in studies of appetite in cancer and chronic illness. It lasts minutes in the blood, which is why no infusion has become a treatment ¹