175graphs every 3 months, and pubertal staging was assessed from these photographs.
It was observed that the first sign of puberty (either breast development or appear-
ance of pubic hair) appeared in 95 % of girls between the age 8.5 and 13 years, with
a mean age of 10.5 year and standard deviation of 1 year. Similarly, 228 British
boys were followed up with clinical photographs every 3 months, and it was shown
that 95 % of boys had onset of genital development (testes, penis, and scrotum)
between 9.5 and 13.5 years of age, with a mean age of 11.5 years and standard
deviation of 1 year. From these data, the cutoffs for the definition of abnormal onset
of pubertal development were derived. However, the major shortcoming of this
study was that the children recruited for the study were residents of children’s home
and belonged to lower socioeconomic strata. Further, the assessment of pubertal
status was based on photographs rather than physical examination.- How were the age cutoffs for precocious puberty defined?
The age of onset of puberty in a population is normally distributed (bell- shaped
curve with a Gaussian distribution). In the studies by Tanner and Marshall, it
was shown that the mean age of onset of puberty was 10.5 years in girls and
11.5 years in boys, with a standard deviation of approximately 1 year.
Considering the normal range of age of pubertal onset as mean ± 2.5 SD, any
sign of pubertal development before the age of 8 years in girls or before 9 years
in boys (−2.5 SD from the mean, i.e., 10.5–2.5 years and 11.5–2.5 years,
respectively) suggests precocious puberty.- Does cutoff for the diagnosis of precocious puberty require redefinition?
In a large cross-sectional study involving 17,000 American girls between the age
of 3 and 12 years [Pediatric Research in Office Settings (PROS) study], it was
observed that the mean age of onset of Tanner 2 breast development was
9.96 ± 1.82 years in White girls and 8.87 ± 1.93 years in African–American girls,
as opposed to mean age of 11.15 ± 1.1 years reported earlier by Tanner and
Marshall. Based on these data, Lawson-Wilkins Pediatric Endocrine Society sug-
gested that the cutoffs for defining precocious puberty should be lowered to
7 years in White girls and 6 years in African–American girls. However, the dis-
sociation between the age of onset of pubertal development as evidenced by ear-
lier age of onset of breast development without change in the age of menarche
raised a question on the accuracy of assessment of breast staging (by visual
inspection) in the PROS study. Thereafter, a recent study involving Black girls
between the age 6 and 8 years and White girls between the age 7 and 8 years with
precocious puberty showed that 88 % had “idiopathic precocious puberty.” These
girls with “idiopathic precocious puberty” were likely to have normal variant of
puberty. However, in the same study, it was shown that 12 % of these girls had an
organic cause of sexual precocity. Therefore, decreasing the age of evaluation of
precocious puberty to <7 years in White and <6 years in Black girls will result in
underdiagnosis of organic cause of precocious puberty in these girls. Despite
limitations of the available data, the cutoffs of 8 years for girls and 9 years for
boys are still widely used for defining precocious puberty in clinical practice.6 Precocious Puberty