What Is HGH? Human Growth Hormone Explained
Human growth hormone (HGH, somatropin) is a 22-kDa peptide hormone of 191 amino acids, produced by the anterior pituitary. It drives growth during childhood and adolescence and continues to influence body composition, tissue repair and metabolism in adults, largely indirectly through IGF-1 made in the liver. Secretion is pulsatile rather than steady — pulses come roughly every 2 to 2.5 hours, and up to 70% of daily output arrives with the first episode of slow-wave sleep — which is why a single blood measurement says almost nothing on its own. Growth hormone is a prescription medicine with specific approved indications. In the United States, distributing it for uses other than an authorised medical condition is a federal criminal offence under 21 U.S.C. § 333(e), carrying up to five years in prison.
What growth hormone does
In children, growth hormone drives skeletal growth, which is its most visible role. In adults the picture is subtler: it influences body composition, contributes to tissue maintenance and repair, and affects how the body handles fat and glucose. Much of its effect is indirect, mediated through IGF-1 produced largely in the liver in response to GH signalling.
Why a single blood test tells you little
Growth hormone is not released continuously. Pulses arrive roughly every 2 to 2.5 hours, separated by intervals during which the hormone is cleared from circulation — and up to 70% of a day's total secretion comes with the first episode of slow-wave sleep. Between pulses, levels are genuinely low in a completely healthy person.
So a random GH measurement can read low in someone whose secretion is entirely normal, purely because of when the blood was drawn. This is why deficiency is assessed with stimulation testing alongside IGF-1 rather than a single GH level, and why any marketing that leans on a "low GH result" from one isolated draw is not saying what it appears to be saying.
What controls it
Two hypothalamic peptides do most of the regulating, pulling in opposite directions: growth hormone releasing hormone (GHRH) promotes release, and somatostatin suppresses it. Their interplay, plus feedback from GH and IGF-1, is what produces the pulsatile pattern rather than a steady level.
Release is also sensitive to metabolic state. It is stimulated by hypoglycaemia and suppressed by overeating, hyperglycaemia and obesity — which is worth knowing before reading much into any single result.
Levels decline with age — what that does and does not mean
Growth hormone secretion falls gradually across adult life. This is well established and is the observation the entire anti-ageing marketing category is built on.
The inference drawn from it is where the problem lies. That a hormone declines with age does not establish that restoring it to youthful levels is beneficial, safe, or advisable — it is a correlation being read as a prescription. Growth hormone is approved for diagnosed deficiency, and treating age-related decline as if it were that condition is not a position the approved indications support.
Frequently asked questions
This article describes what growth hormone is. It does not assess whether anyone should take it, it gives no dosing, and it is not a substitute for an endocrinologist. It does not work through the adverse effects of growth hormone therapy or the monitoring supervised treatment requires — both are real and both belong with a prescriber and the approved label rather than a reference page. The legal position described here is the United States federal one and does not describe any other country. Anyone considering GH for ageing or performance should note that this is precisely the use the statute excludes, and that the offence it defines is distribution rather than possession — which does not make obtaining it lawful, but does mean the risk falls hardest on whoever supplied it.
Part of the HGH & Growth Hormone Guide.