Urinary growth hormone estimation in diagnosing severe growth hormone deficiency

Urinary growth hormone was measured in 54 children with short stature who had growth hormone deficiency that was initially diagnosed pharmacologically (arginine and L-dopa) and physiologically (mean growth hormone concentration during sleep evaluated twice). Based on the growth hormone response to pharmacological tests the subjects were subdivided into three groups: group A, 20 subjects with normal response (peak concentration > 8 micrograms/l); group B, 20 subjects with response between 4 and 8 micrograms/l; and group C, 14 subjects with response < 4 micrograms/l. In group A four subjects had an abnormally low nocturnal mean growth hormone concentration (< or = 3.3 micrograms/l). In group C seven subjects 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 between serum nocturnal mean growth hormone values and urinary growth hormone in all subjects. Mean (SD) concentrations of urinary growth hormone 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 hormones below the lower limit of the range in group A, specificity and sensitivity of urinary growth hormone was 100% and 35% respectively. Sensitivity for groups B and C were 5% and 78% respectively. When considering only the subjects of group C with pathological magnetic resonance findings, sensitivity increased to 100%. In the four subjects of group A with mean growth hormone concentration < or = 3.3 micrograms/l, specificity decreased to 80%. It is concluded that urinary growth hormone assay is characterised by a sensitivity too low to be regarded as improving the traditional diagnostic approach to define growth hormone deficiency, unless it is used to identify subjects with the most severe deficiencies.