In this presentation, Griffin explains the basic mechanisms of catch up growth. Catch up growth follows a variety of nutritional or non-nutritional events that slow the normal rate of growth, and is characterized by faster than expected growth once the insult is over. Tanner’s Time Tally Model, The Growth Plate Hypothesis and the Neuroendocrine Hypothesis have all been used to explain catch up growth. Of the three, the Neuroendocrine Hypothesis is the most extensively studied and has gained wide acceptance. The mechanisms of hepatic growth hormone resistance were also explained in this presentation. Growth arrest in malnutrition is likely to be a combination of increased ghrelin and growth hormone coupled with increased deacetylase sirtuin- 1 (SIRT1) and fibroblast growth factor 21 (FGF21).