CONSTITUTIONAL DELAY OF GROWTH AND PUBERTY
Delayed puberty is defined as the absence of testicular enlargement in boys or breast development in girls 2 to 2.5 standard deviations (SDs) later than the population average. Although a single definition does not apply to all populations, a practical definition for girls is the lack of breast development by age 13 years and for boys, a testicular volume of less than 4 mL by 14 years.1,2,3 Because of a downward trend in pubertal timing in the United States4,5 and other countries6,7 and differences in pubertal timing among ethnic groups, some advocate for updated definitions with younger age cutoffs for the general population, or perhaps for particular countries or ethnic groups. Development of pubic hair is usually not considered in the definition because pubarche may result from maturation of the adrenal glands (adrenarche), and onset of pubic hair can be independent of hypothalamic-pituitary-gonadal (HPG) axis activation.
Constitutional delay of growth and puberty (CDGP) is the term used to characterize a normal variant of growth seen in healthy, and often short, children who manifest a pubertal delay alongside a delayed bone age. The etiology of CDGP is unknown, but it has a strong genetic basis. Fifty to 80% of variation of the timing of puberty in humans is due to genetic factors, and 50% to 75% of individuals with CDGP have a family history of delayed puberty.8,9 The inheritance of CDGP is variable but most often consistent with an autosomal dominant pattern, with or without complete penetrance. Based on the expected distribution of the age of pubertal onset, delayed puberty is expected in at least 2.3% of both boys and girls. However, the vast majority of patients seen in specialized care are boys.
CDGP accounts for approximately 65% of pubertal delay in boys and approximately 30% in girls.3,8 Although CDGP is particularly common in boys, there may also be a referral bias for males because of an expressed or perceived greater psychologic pressure on small and sexually immature boys.10 Also the fact that the first signs of puberty are more easily detected in girls (breast budding vs testicular enlargement) may skew the practice toward more frequent referral of boys, although the recommendation is to refer both genders with first signs appearing more than 2 to 2.5 SD beyond the mean, that is, after age 13.5 in boys and 13.0 in girls. As a consequence of skewed referral practice generating male predominance of CDGP, one would expect referred girls to show more severe delay of puberty. In one study based on retrospective evaluation of hospital charts of adolescents referred to an endocrinology clinic for pubertal delay, the girls were more severely affected, as evidenced by their greater bone age delay.8 Because CDGP presents with both short stature and pubertal ...