Essentials for diagnosis
(1) Secondary sex characters appear below the age of 8 in girls and 9 in boys. Generally, mammary development and pubic hair appear in succession in girls. Mostly, pubic hair comes out with the development of external genital organs. Finally, menstrual onset and axillary hair appear. At the beginning, menstrual cycle is irregular and no ovulation exists while menstrual cycle becomes regular and pregnancy is possible after complete maturation of ovary. Boys show simultaneous premature enlargement of penis and testes. Later on, erection of penis is possible. Pubic hair, acne and low and deep voice appear. Spermioteleosis and nocturnal emission may exist at the age of 5 to 6. These boys are physically stronger than other boys of the same age.

(2) During sexual development, height and weight increase very quickly and skeletal development speeds up both in boys and girls. Accelerated development of skeleton results in premature bone closure, finally giving rise to short height compared with ordinary people. The development of intelligence and teeth keeps in step with the age.

(3) Physicochemical examinations and tests show markedly elevated contents of plasma follicule-stimulating hormone (FSH), luteotropic hormone (LH), estradiol (E2) and luteinizing hormone-releasing hormone (LH-RH). X-ray film of eutopic carpal bone indicates that maturity of bone age exceeds the real age, matching with sexual precocity.