A bone age of 1.5 years means late epiphyseal closure, and may also mean the presence of growth hormone deficiency, hypothyroidism and other diseases. 1. Late epiphyseal closure: Small for age usually occurs in children, which means that the age of the bones does not match the actual age, and the epiphyseal closure time of children will be relatively later, and the time of bone growth will be relatively longer. 2. Growth hormone deficiency: Growth hormone is one of the important hormones secreted by the pituitary gland of the hypothalamus to promote children’s growth and bone development. When there is a lack of growth hormone in a child’s body, it will lead to slow development and small bone age. 3. Hypothyroidism: Thyroid hormone can promote growth by promoting protein synthesis, which together with growth hormone promotes children’s development. Therefore, when the thyroid gland is hypothyroid, it will affect the growth and development of children, resulting in slow growth and small bone age. When a child’s bone age is 1.5 years younger, he or she should consult a doctor in time to clarify whether there are pathological factors under the guidance of a professional doctor. When pathological factors exist, they should be actively treated so as not to affect the normal growth and development of children.