a) When puberty occurs at an unusually early age it is called precocious puberty. Puberty is considered precocious in girls if they show the signs of sexual maturity (onset of menstruation, developments of breasts, and appearance of pubic hair) when they are below 8 years of age. In case of boys, puberty is considered to be precocious if they show signs of sexual maturity (appearance of pubic hair, genital enlargement) below the age of 9 years. Early onset of puberty results in short adult stature and emotional distress.
b) Puberty is said to be delayed when it does not occur even after the normal age (10-15 years for girls and 9-15 years for boys approximately) has passed. There is no physical or hormonal signs of maturity. Common causes for delayed puberty are malnutrition, systemic disease, tumours in the pituitary gland, or defects in the endocrine glands that trigger the onset of puberty.