What causes precocious puberty?

What is precocious puberty?

Developing the physical changes associated with puberty unusually early is known as precocious puberty.In a girl, these changes are the development of breasts, pubic and/or armpit hair before eight years of age, or starting periods (menarche) before nine years of age.In a boy, the changes are enlargement of the testicles, scrotum and ..... and development of pubic and armpit hair before nine years of age.