A 10-year-old girl exhibits high level of physical development (Μ + 3σ), her body length increased by 10 cm within a year (which is double the norm for her age group), the number of permanent teeth corresponds with the age norm (20), the development of her secondary sex characteristics is three years ahead of her age (Ма, Р, Ах, Menarche). Development rate ahead of her biological age can occur due to: