Exercise Test

INDICATION

Used in a child with definite growth retardation preferably as assessed by reduced growth velocity and a random serum growth hormone (GH) of <15 mU/l. It is a physiological screening test used before formal testing of GH secretion (e.g. insulin tolerance test, arginine stimulation test).

METHOD

1. If child has difficult veins, cannulate before the test (butterfly is sufficient).
2. Take blood sample for GH (into a red top Vacutainer) at T = 0.
3. Take child to the outpatients staircase and note the time
4. Child should then run up and down the first flight of stairs, as hard and as fast as possible, for at least 10 mins and until the child becomes breathless and moderately fatigued
5. Take blood sample for GH 30 mins after the onset of exercise

INTERPRETATION

A normal GH response of > 15 mU/l (5.7 ng/ml) absolves the endocrinologist of any further investigation of GH deficiency. It excludes the need for proceeding to the more laborious and hazardous formal tests. A subnormal response (GH < 15 mU/l) means the child should be considered for a formal test though a repeat exercise test may be valuable (see below).

SENSITIVITY AND SPECIFICITY

A child with GH deficiency will not respond to this test. The percentage of children who are not GH deficient and who show a normal response varies depending on the test used and the peak GH value taken as "normal". Values vary from 68-91%. Repeating the test can also improve the detection rate of normals from 80-92%.

REFERENCE

Milner R.D.G. & Burns E.C., Arch. Dis. Child. 57, 944-947 (1982).