Tests for growth hormone secretion.

Tests for growth hormone secretion SIR,-We were interested in the correspondence between Dr Addy and Professor Brook and Dr Hindmarsh on detecting organic illness through assessment of height velocity .' 2 The question, however, is academic and their arguments theoretical since, as we have recently shown, the assessment of height velocity in individuals is so imprecise as to be clinically meaningless. There is effectively no correlation between successive velocities, so that a 12 month velocity cannot possibly identify anyone.3'4 The Wessex Growth Study provides a practical demonstration of the problem. Thirty (17%) of the original cohort of 174 school entrants below the third height centile had identifiable organic disease. Eighteen of these were monitored over a period of three years alongside a cohort of 78 short 'normal' children in whom all pathology had been excluded. The height velocity of four of the short 'normal' children and two of those with organic disease was deemed to be on or below the third centile for velocity after the first year. Over the next 12 months, two of the short 'normal' subjects, and three of those with organic disease, were growing at a rate below the third centile, but the identity of the 'poor growers' changed from year one to year two. We should abandon the notion that low 12 month velocities will effectively identify pathology. The children in the Wessex Growth Study with organic causes of short stature were identified at the beginning of year one on the basis of height screening alone.