Somatropin (HGH)

Growth hormone axis

Also known as Human growth hormone, HGH, Norditropin, Genotropin, Humatrope, Omnitrope

Growth hormone itself, rather than something that asks your pituitary to make more of it.

How it works

Recombinant human growth hormone, identical in sequence to the pituitary hormone. It acts directly at the GH receptor and more importantly for most of its effects, drives the liver to produce IGF-1. Unlike a secretagogue it does not depend on your own pituitary having anything left to give, and equally it does not respect the feedback loop that would normally limit the response.

SubcutaneousIntramuscular

In the body

Half-life

2.6 hours

Time to peak

3.5 h

90% gone after

8.6 h

Builds up to

1×

Steady state after about 13.2 h at daily.

Shape of a single dose, modelled as one compartment with first-order absorption. The peak is normalised to 100% because bioavailability and volume of distribution are not published for most of these compounds.

2.6 hours after subcutaneous injection, peaking at about 4 hours. Short, but misleading on its own: the effects run through IGF-1, which has a half-life measured in hours to days, so what the body does lasts far longer than the hormone is present. The curve is drawn with a 3.5 hour peak rather than the published 4, because absorption from the subcutaneous depot is slower than clearance and a one-compartment model cannot place a peak later than that, the shape is right, the peak is half an hour early.

What happens, and when

0 min, 4 hRising towards peak; the pulse is deliberately brief.
4 h, 12 hFalling, while IGF-1 production in the liver picks up.
12 h, 2 dHormone long gone; IGF-1 is doing the work.

Doses

100 mcg, 300 mcgdailyApproved label

0.1-0.3 mg daily, or roughly 0.3-0.9 IU, as the starting dose for adult-onset growth hormone deficiency. Titrated monthly against IGF-1 rather than by feel.

300 mcg, 1 mgdailyApproved label

Maintenance for diagnosed deficiency, not exceeding 1 mg (3 IU) daily. Women on oral oestrogen generally need more; requirement falls with age.

667 mcg, 1.333 mgdailyCommunity practice

The 2-4 IU daily range used non-medically. Above the licensed maximum, and the glucose and fluid-retention effects scale with it.

Vial sizes

5 mg10 mg15 mg

Commonly treated as good for 28 days refrigerated once reconstituted.

Side effects

Fluid retention, which is the commonest early effect and is dose-dependent
Carpal tunnel syndrome and paraesthesia
Joint and muscle aches
Insulin resistance and rising fasting glucose
Hypothyroidism, which can be unmasked rather than caused
Benign intracranial hypertension, rarely
Monitor: IGF-1, which is the only meaningful measure of whether the dose is right
Monitor: fasting glucose and HbA1c
Monitor: thyroid function

Cautions

Any active malignancy
Acute critical illness following surgery, trauma or respiratory failure
Proliferative diabetic retinopathy
Children with closed epiphyses, for growth purposes

Status

Prescription-only everywhere, and specifically scheduled in several countries including the United States, where distribution for non-medical use is a federal offence. Banned in sport at all times.

Sources

Reference information for personal record-keeping. Not medical advice, and not a recommendation to use any of these compounds.