URINARY GROWTH-HORMONE ESTIMATION IN DIAGNOSING SEVERE GROWTH-HORMONEDEFICIENCY

Urinary growth hormone was measured in 54 children with short stature who had growth hormone deficiency that was initially diagnosed pharmac ologically (arginine and L-dopa) and physiologically (mean growth horm one concentration during sleep evaluated twice). Based on the growth h ormone response to pharmacological tests the subjects were subdivided into three groups: group A, 20 subjects with normal response (peak con centration > 8 mu g/l); group B, 20 subjects with response between 4 a nd 8 mu g/l; and group C, 14 subjects with response < 4 mu g/l. In gro up A four subjects had an abnormally low nocturnal mean growth hormone concentration (less than or equal to 3.3 mu g/l). In group C seven su bjects had multiple pituitary hormone deficiency and abnormal magnetic resonance imaging. All subjects had urine collected from 8.00 pm to 8 .00 am for 4-5 consecutive nights. A positive correlation was found be tween serum nocturnal mean growth hormone values and urinary growth ho rmone in all subjects. Mean (SD) concentrations of urinary growth horm one were similar in groups A (18.0 (9.5) ng/g creatinine) and B (13.6 (5.9) ng/g creatinine), but significantly higher than that of group C (3.4 (3.7) ng/g creatinine). Considering as abnormal urinary growth ho rmones below the lower limit of the range in group A, specificity and sensitivity of urinary growth hormone was 100% and 35% respectively. S ensitivity for groups B and C were 5% and 78% respectively. When consi dering only the subjects of group C with pathological magnetic resonan ce findings, sensitivity increased to 100%. In the four subjects of gr oup A with mean growth hormone concentration less than or equal to 3.3 mu g/l, specificity decreased to 80%. It is concluded that urinary gr owth hormone assay is characterised by a sensitivity too low to be reg arded as improving the traditional diagnostic approach to define growt h hormone deficiency, unless it is used to identify subjects with the most severe deficiencies.