ESPE Abstracts (2018) 89 SS1.2

Fascinating Growth Phenomena: What Causes Individual Catch-up Growth and Population Secular Change?

Jan M Wit

Leiden University Medical Center, Leiden, Netherlands

Catch-up growth (CUG) is characterized by a period of supranormal height velocity following a transient period of growth inhibition. The two classical hypotheses on the mechanism are the neuro-endocrine hypothesis (a central mechanism that would recognize the degree of mismatch between actual size and target size) and the growth plate hypothesis (local regulation of growth according to a preset cellular program of senescence, characterized by decreasing growth proliferation rate). Unilateral CUG in animal experiments argue against the neuro-endocrine hypothesis, and the fast growth in type A CUG argues against the growth plate hypothesis. Recent data indicate that various regulatory factors may be involved in CUG after malnutrition, including Hypoxia-Inducible Factor 1 (HIF1), mTOR, Sirtuins (class III histone deacetylases), microRNAs, the GH-IGF-1 axis, Ghrelin, Leptin and insulin. Positive secular changes in body size and tempo of growth have occurred in most western countries since 1850, generally considered as an indicator of better nutrition, hygiene and health status. Secular increase is most prominent at 4–11 years of age. At the completion of the secular trend in various countries adult height has increased up to 20 cm and is reached >8 years earlier. However, attained mean adult heights are different, suggesting that besides environmental influences also genetic or geographic factors play a role, and possibly also culturally engrained nutritional habits. The magnitude of secular trend is relatively strong in individuals of low socio-economic background, reducing social class differences in height. Regarding the mechanism, epigenetic processes (in foetal life or early infancy) seem most plausible. The extensive time interval and magnitude of secular trend, the different stages of secular trend in high income and many low- and middle income countries, on top of the presumed effect of genetic and geographic variations, make it difficult to defend the concept of a ‘global growth standard’.

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