MKRN3 appears to act as a "brake" on the central hypothalamic-pituitary access. Thus, loss of function mutations of the protein allow early activation of the GnRH pathway and cause phenotypic CPP. Patients with a MKRN3 mutation all display the classic signs of CCP including early breast and testes development, increased bone aging and elevated hormone levels of GnRH and LH. Diagnosis
Studies indicate that breast development in girls and the appearance of pubic hair in both girls and boys are starting earlier than in previous generations. As a result, "early puberty" in children as young as 9 and 10 is no longer considered abnormal, particularly with girls. Although it is not considered as abnormal, it may be upsetting to parents and can be harmful to children who mature physically at a time when they are immature mentally.No age reliably separates normal from abnormal processes in children, but the following age thresholds for evaluation are thought to minimize the risk of missing a significant medical problem:

Breast development in boys before appearance of pubic hair or testicular enlargement
Pubic hair or genital enlargement (gonadarche) in boys with onset before 9 years
Pubic hair (pubarche) before 8 or breast development (thelarche) in girls with onset before 7 years
Menstruation (menarche) in girls before 10 yearsMedical evaluation is sometimes necessary to recognize the few children with serious conditions from the majority who have entered puberty early but are still medically normal.
Causes
Early pubic hair, breast, or genital development may result from natural early maturation or from several other conditions. Central
If the cause can be traced to the hypothalamus or pituitary, the cause is considered central. Other names for this type are complete or true precocious puberty.Causes of central precocious puberty can include:

hypothalamic hamartoma produces pulsatile gonadotropin-releasing hormone (GnRH)
Langerhans cell histiocytosis
McCune–Albright syndromeCentral precocious puberty can also be caused by brain tumors, infection (most commonly tuberculous meningitis, especially in developing countries), trauma, hydrocephalus, and Angelman syndrome. Precocious puberty is associated with advancement in bone age, which leads to early fusion of epiphyses, thus resulting in reduced final height and short stature.Adrenocortical oncocytomas are rare with mostly benign and nonfunctioning tumors. There have been only three cases of functioning adrenocortical oncocytoma that have been reported up until 2013. Children with adrenocortical oncocytomas will present with "premature pubarche, clitoromegaly, and increased serum dehydroepiandrosterone sulfate and testosterone" which are some of the presentations associated with precocious puberty.Precocious puberty in girls begins before the age of 8. The youngest mother on record is Lina Medina, who gave birth at the age of either 5 years, 7 months and 17 days or 6 years 5 months as mentioned in another report. "Central precocious puberty (CPP) was reported in some patients with suprasellar arachnoid cysts (SAC), and SCFE (slipped capital femoral epiphysis) occurs in patients with CPP because of rapid growth and changes of growth hormone secretion. "If no cause can be identified, it is considered idiopathic or constitutional.