Girls between the ages of three and thirteen were selected, and they were divided into two groups: the "Before COVID-19 pandemic" group, which included CPP cases from April 7, 2019 to April 6, 2020, and the "After COVID-19 pandemic" group, which included CPP cases from April 7, 2020 to April 6, 2021. CPP was defined as breast development at <7 yr and 6 mo of age, pubic hair development, labia minora pigmentation or axillary hair development at < 8yr of age, and menarche at <10 yr and 6 mo of age; basal LH value ≥0.5 mIU/mL or peak LH value ≥5.0 mIU/mL at the time of GnRH stimulation test. Here, PLOD1 is linked to central precocious puberty.