Growth hormone deficiency (GHD) is one of the most common endocrine disorders with short stature in children. GHD is conventionally diagnosed and confirmed by the diminished peak of growth hormone (GH) for provocative testing. It is found that the level of Insulin-like growth factor-1 (IGF-1) and Insulin-like growth factor binding protein-3 (IGFBP-3) is under the influence of GH and reflects the spontaneous endogenous GH secretion. According to the absence of a circadian rhythm, it is possible to take individual measurements of IGF-1 and IGFBP-3 at any time of the day to assess the state of GH instead of subjecting the individual to cumbersome provocative tests. In this book, we review a new clinical method for diagnosing growth hormone deficiency in children and adolescents with short stature.