Day: July 10, 2017

Do Children Grow Overnight?

Patient Presentation
A 14-year-old male came to clinic for his health maintenance examination. He was well and his mother was joking with the pediatrician saying, “He’s really growing. I measured him only 3 weeks ago and he’s already grown an inch since then. I can see it in his pants too because they were fitting a month ago and now you can see his ankles.” The past medical history was non-contributory.

The pertinent physical exam showed a well-appearing male, who was growing at the 50th percentile for height and 75% for weight. He had grown 8.5 centimeters in height over the past 12 months. He was Tanner stage 4 for pubic hair and genitalia. The diagnosis of a healthy male was made. The pediatrician said, “We hear the parents say this often that the kids grow overnight. They certain can have big growth spurts.” Later he was thinking about the conversation and decided to search the literature to see what medical literature might support this idea.

Discussion
Growth is an important vital sign for children. Normal growth patterns usually indicate healthy children and can be reassuring for both the parents and health care providers alike. Children are not usually measured very often by parents or health care providers and therefore the actual growth occurrence is not identified until after the event. Measuring small increments accurately also makes data collection difficult, along with the inconvenience of frequent serial measurements.

A review of various growth parameters in children can be found here.

Learning Point
There is evidence that children do grow over very short periods of time. Rogol writes, “…[T]here is compelling evidence to invoke a pattern characterized by short saltations flanked by longer periods of stasis, both in infant and during the pubertal growth spurt.” When these saltations or periods of rapid growth are averaged over longer periods of time, it can look like growth is a continuous process.

One adolescent male was measured almost daily for 389 consecutive days and was found to have linear growth on only 12 days. This is an average of ~1 day of growth out of 31, but the number of days between the growth days was heterogeneous ranging from 13-100 days. Another study of infants and toddlers, showed discontinuous growth spurts of 0.5-2.5 cm of linear growth separated by no measureable growth for 2-63 days. A third study of infants and toddlers, showed saltatory head circumference growth of 0.2 cm separated by no growth for 1-21 days. These head circumference growth saltations were also coupled to length growth saltations (median 2 days, range 1-8 days).

The mechanism for the saltatory growth for linear growth appears to be the chondrocytic life cycle itself and the changes that occur at the growth plates of long bones. Chondrocytes emerge from their stem cells, undergo proliferation, then a rest phase, then hypertrophy, and finally vascular invasion and mineralization. The timing of each state, especially the resting state and the hypertrophy state where linear growth occurs, is under numerous controlling factors including genetic, hormonal and nutritional. Lampl and Schoen state, “[i]n a sequence of “turn on” and “turn off” mechanisms across the chondrocytic life cycle, the final clonal chondrocyte hypertrophy operates as the cellular basis for saltatory growth, the biological process by which individuals accrue height in discrete spurts (saltations) separated by variable intervals of growth quiescence (stasis), empirically documented at the level of the whole body… and the growth plate itself….” They note that “…variation in saltatory amplitude and frequency characteristics underlie difference in growth rates, tempo, and time-based growth trajectories within and among individuals, including population-distinctive patterns.”

Questions for Further Discussion
1. What are the first signs of puberty?
2. The height spurt occurs during what Tanner stage(s) usually?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Child Development and Growth Disorders.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Lampl M, Veldhuis JD, Johnson ML. Saltation and stasis: a model of human growth. Science. 1992 Oct 30;258(5083):801-3.

Lampl M, Johnson ML. A case study of daily growth during adolescence: a single spurt or changes in the dynamics of saltatory growth? Ann Hum Biol. 1993 Nov-Dec;20(6):595-603.

Robol AD. Growth, body composition and hormonal axes in children and adolescents. J Endocrinol. Invest. 2003; 26:855-860.

Lampl M, Johnson ML. Infant head circumference growth is saltatory and coupled to length growth. Early Hum Dev. 2011 May;87(5):361-8.

Fennoy I. Effect of obesity on linear growth. Curr Opin Endocrinol Diabetes Obes. 2013 Feb;20(1):44-9.

Lampl M, Schoen M. How long bones grow children: Mechanistic paths to variation in human height growth. Am J Hum Biol. 2017 Mar;29(2).

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa