IGF-1

The hormone growth hormone actually works through. The liver makes it in response to growth hormone.

Growth hormone comes in pulses that a single sample would miss entirely; IGF-1 is steady, so it is what growth hormone status is judged on.

It falls steadily with age, so it must be read against an age band rather than one adult range. Poor nutrition, liver disease and untreated diabetes all lower it independently of growth hormone.

Worth discussing a value well outside the range for your age.