The development of any sign of secondary sexual maturation at an age earlier than 2,5 standard deviations less than the expected age of pubertal onset is named by precocious puberty. These ages depend on the location or the country. In North America, 9 years for boys and 8 years for girls. Girls are more common than boys (approximately five times). Seventy percents of cause precocious puberty in girls is idiopathic. These girls are taller than their peers as children but ultimately are shorter as adults owing to the premature fusion of the long bone epiphyses.

Female precocious puberty is divided into two: heterosexual precocious puberty and isosexual precocious puberty

Heterosexual Precocity

The development of secondary sexual characteristics opposite those of the anticipated phenotypic sex, it results from:

1. Virilizing neoplasms.
2. Congenital adrenal hyperplasia.
   It result from a defect of the adrenal enzyme 21 hydroxylase leading to excessive androgen production. These may cause the birth of a female with ambigous genitalia. It also can cause premature pubarche and an adult disorder resembling polycystic ovary syndrome (less severe form of this defect). Replacement of cortisol with a related glucocorticoid and surgical correction of any anatomic abnormalities in the first few years of life can be used for treat this.
3. Exposure to exogenous androgens.
   Most commonly an arrhenoblastoma or adrenal in origin. We can treat this by surgical removal

Isosexual Precocious Pubert

Premature sexual maturation that is appropriate for the phenotype of the affected individual that results in the development of the full complement of secondary sexual characteristics and increased levels of sex steroid. True isosexual precocity involve the hypothalamic-pituitary-gonadal axis (premature activation).

Pseudoisosexual precocity result from elevation of estrogen levels and cause sexual characteristib maturation without activation of the hypothalamic-pituitary axis.


Laboratory Test Used Selectively to Evaluate female Precocious Puberty

1. Radiologic.
   
   • Serial bone age (isosexual precocity)
   • MRI or CT of brain with optimal visualization of hypothalamic region and sella tursica (true isosexual precocity)
   • For heterosexual precocity and pseudoisexual precocity, we can use MRI, CT or USG of abdomen, pelvis, or adrenal gland
2. Laboratory
   
   • LH and FSH
   • DHEA-S ( Dehydroepiandrosterone sulfate), testosterone (heterosexual precocity)
   • TSH, free T4 (isosexual precocious puberty)
   • 17-OH progesterone, 11-deoxycortisol (suspected congenital adrenal hyperplasia causing heterosexual precocity)
   • GnRH stimulation test : LH measurement after 100 mcg of GnRH given intravenously to differentiate gonadotropin-dependent from gonadotropin-independent isosexual precocity

(by the doctor rend-san)