Growth hormone (GH): the GH/IGF-1 axis explained

A hormone released in pulses

Growth hormone (GH, or somatotropin) is produced by the somatotroph cells of the anterior pituitary. Its secretion is pulsatile: it comes in peaks, a large share of them during deep sleep, with low concentrations in between.

Three main signals control this secretion:

• GHRH: a hypothalamic hormone that stimulates GH release.
• Somatostatin: a hypothalamic hormone that inhibits it.
• Ghrelin: a peptide made mainly by the stomach, identified in 1999 as the natural ligand of the GH secretagogue receptor.

IGF-1, the relay for many effects

Many of GH’s effects are mediated by IGF-1, produced mainly by the liver in response to GH. IGF-1 in turn exerts negative feedback on the hypothalamus and pituitary. This loop is why the axis is read as a whole rather than from a single measurement.

GH deficiency: a specialist diagnosis

In adults, Endocrine Society and AACE guidelines reserve a diagnosis of GH deficiency for specific clinical contexts (hypothalamic-pituitary disease, or a history of surgery or radiotherapy, for example). Because secretion is pulsatile, a single GH measurement is not enough: diagnosis usually relies on stimulation tests carried out in a specialist setting.

When indicated, treatment uses recombinant human GH, a prescription medicine monitored by an endocrinologist. These guidelines do not support its use for ageing or performance.

GH, secretagogues and anti-doping rules

The World Anti-Doping Agency (WADA) Prohibited List classifies GH among peptide hormones prohibited at all times. It also covers GHRH analogues and GH secretagogues, including ghrelin mimetics.

Velia Labs sells neither GH nor GH secretagogues. The catalog lists the references we offer, all intended for laboratory research only. This article is not medical advice: any question about treatment belongs with a doctor.

Sources

• Müller et al., Physiol Rev 1999: neuroendocrine control of GH secretion
• Kojima et al., Nature 1999: the discovery of ghrelin
• Endocrine Society 2011: adult GH deficiency
• AACE 2019: management of GH deficiency
• WADA: the Prohibited List