Growth hormone (GH)

A random value has no useful range because the hormone is released in bursts; labs print a cut-off for the nadir during a glucose suppression test (commonly below 0.4 or 1 ug/L) or for the peak in a stimulation test, and older UK reports use mU/L, where 1 ug/L equals 3 mU/L.

Growth hormone is made by the pituitary gland in short bursts, mostly during deep sleep and after exercise, with almost none in between. In children it drives growth in height; in adults it helps maintain muscle, bone and body composition. Because of the bursts, a single random level says little and it is usually measured during a formal test.

It is requested in specialist clinics when too much growth hormone (acromegaly, or gigantism in children) or too little (short stature in children, pituitary failure in adults) is being looked into. In adults IGF-1 is the usual first test, and growth hormone is then measured during a glucose suppression or stimulation test.

• A burst of normal release, during sleep, after exercise, after fasting or with stress
• A pituitary growth that makes growth hormone (acromegaly)
• Poorly controlled diabetes, liver disease and kidney disease
• Low body weight and eating disorders
• Puberty and pregnancy
• Growth hormone injections used in treatment or misused in sport

• Between bursts, which is most of the day
• Pituitary damage from surgery, radiotherapy, tumours or head injury
• Heavier body weight
• Older age, in the general population
• Steroid medicines and an underactive thyroid

• A single random value can be high after exercise or fasting or almost zero at rest in the same healthy person
• UK labs have switched from mU/L to ug/L over the years, so older results look three times larger
• Different assays give different numbers

Rarely useful as a single random sample. It is normally measured at set times during a glucose suppression test or a stimulation test in clinic, resting and fasting.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.