THE USE OF AN AUTOMATED MICROSAMPLING SYSTEM FOR THE CHARACTERIZATIONOF GROWTH-HORMONE PULSATILITY IN NEWBORN BABIES

To overcome the difficulties of studying hormone pulsatility in the ne wborn, we have developed an automated microsampling system that permit s the measurement of hormones in small prediluted samples of blood (40 mu L) taken at 10-min intervals over 12 h. The system has been valida ted in adult volunteers, and the error attributable to the dilution wa s <4%. Using this method in 10 preterm babies, we have been able to de scribe pulsatile changes in GH and have demonstrated a clear postprand ial elevation in GH levels peaking 60 min after a feed. Fourier transf orm analysis indicated a pulse periodicity of 180 min in babies who we re appropriate for gestational age (n = 6), but faster, co-dominant pu lse periodicities of 90-100 and 140 min in babies who were small for g estational age (weight and length below the 10th centile) (n = 4). The re was no significant difference between mean, peak, and baseline GH l evels between the two groups.