Small bone age does not mean late growth. Bone age refers to the relationship between the appearance and closure of the skeletal nucleus and the actual age, which varies from individual to individual. Small bone age is common in childhood, which means that children’s bones will close relatively late, and bone development can continue and grow taller. The causes of small bone age include the following possibilities: 1, imperfect dietary structure during growth and development, too little calcium intake, which may affect children’s bone development; 2, due to hypothalamus or pituitary gland dysfunction, resulting in reduced synthesis or secretion of growth hormone, children’s growth rate will be lower than normal; 3, underdeveloped thyroid gland, resulting in abnormal secretion of thyroid hormones, which will affect children’s bone growth and development. Therefore, if a child has small bone age or late growth during the growth process, it is recommended to go to the hospital in time to clarify the cause of small bone age through X-ray and give targeted treatment.