Short-term growth at adolescence in healthy girls

In the last decade, most investigators found that growth measured on a daily or weekly basis is a non-linear process, but its precise pattern has not yet been fully determined. Data are particularly scarce during puberty. On this basis we evaluated the daily growth in 10 healthy girls during their adolescent growth spurt with replicated height measurements over a period of 128-150 days. The technical error of measurement in each girl varied between 0.08 and 0.12 cm. A jump-preserving smoothing technique based on the technical error with a hard rejection criterion was used. Growth was defined as any increment between two consecutive smoothed values greater than 6 times the standard deviation of the difference of two consecutive smoothed values under the non-growth (stasis) assumption. Steep changes in height were conventionally defined as any 1-day increment greater than 0.3 cm. Results: All girls showed stasis periods, steep changes and days with a continuous growth with a wide range of daily increments in height. The number of stasis periods in each girl varied between three and seven, lasting between 7 and 22 consecutive days. The number of steep changes in each girl ranged between one and four with a mean amplitude between 0.37 and 0.52 cm. The sum of these steep changes calculated in each girl as a percentage of total growth during the study period ranged from 15.3 to 42.9%; the remaining growth was due to continuous growth. Rhythms or cycles were not found. Conclusion: Short-term growth during the pubertal growth spurt in these healthy girls is an irregular and discontinuous process, composed of three types of events: stasis, steep changes and continuous growth periods with a wide individual range of daily height increments.