Epidemiology

The prevalence of precocious puberty is difficult to estimate but has been reported at between 1 in 500-5000 children.[3] Central precocious puberty (CPP) affects girls 5 to 10 times more commonly than boys.[3][4][5]​​​​ The prevalence of CPP was found to be 0.2% in girls but only 0.05% in boys over a 9-year period in one European study.[6]​ This may be because activation of the hypothalamo-pituitary-gonadal axis requires a lower dose of gonadotrophin-releasing hormone (GnRH) in girls.[7] In the US, the number of girls diagnosed with precocious puberty is rising but there are no reliable data on the incidence. One study showed that 10% to 23% of 7-year old girls (depending on race and ethnicity) have breast development, but the proportion who have the type of progressive precocious puberty that might require treatment is likely much lower.[8][3]​​ A repeatedly observed association is between an earlier age of presentation and the likelihood of an organic cause.[9]

Several factors affect the age of onset of puberty, although it primarily follows a familial pattern. A similarity in the age at onset of puberty between girls and their mothers, especially with that of menarche, is known. However, the process can be influenced by environmental factors - particularly nutrition, ethnicity, and chronic disease.

Secular trends demonstrate that in girls, the age at menarche (a late event in female puberty) has decreased considerably in the past century, particularly in western countries,​​ although there has been little further change since the late 1900s.[10][11]​​ One 2005 study in the Netherlands showed a levelling off in the age of onset of puberty; however, evidence is conflicting, with some later studies pointing to an ongoing reduction in the age of breast development in girls.[12][13][14]​​​ There is less evidence that the age of onset of puberty in boys has changed over time,​​ although this may be because the onset and completion of puberty in boys is less well defined and documented compared with the documentation of menarche in girls.[15][16]

Typically, girls of African or Caribbean origin have a younger age of menarche (by approximately 6 months) than white girls.[17]​ The mean age of menarche decreased by 3 months in white girls compared with 5.5 months in girls of African or Caribbean descent between 1960 and 1990 in the US.[18]

An improved socioeconomic status, health care, nutrition, and migration can also influence the genetic predisposition and secular trends. The frequency of obesity in children has doubled since 1980; moderate obesity is associated with an earlier age of menarche.[11][19][20][21]​​​​ Oestrogenic agents in cosmetics and food products have also been implicated in causing an earlier age of puberty.[22]

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