Bone Age in Endocrinology - Part 1: Methods of Bone Age Assessment

Bone age assessment is an essential competency for endocrinology residents, guiding the diagnosis and management of growth disorders, pubertal abnormalities and endocrine conditions. This review is presented in two parts: Part 1 focuses on the methods of bone age assessment, while Part 2 addresses its clinical utility and applications. The Greulich and Pyle (G&P) atlas is widely used for its simplicity, while the Tanner-Whitehouse (TW) method offers a more detailed, scoring-based approach but requires more time. In younger children, proximal ossification centres are more informative, whereas distal centres are more informative in older adolescents. TW3 generally estimates slightly younger ages than TW2, and G&P tends to score younger than TW2. Emerging tools-such as automated image analysis, content-based image retrieval and ultrasonography-promise efficiency gains but face challenges of operator dependence and variable reliability. Advances like BoneXpert have improved standardization and reproducibility, yet traditional G&P and TW methods remain central in endocrine practice due to their accessibility, validated references and widespread familiarity.