Paula J. Adams Hillard, MD


December 30, 2008

Puberty and Menarche

Conventional textbook teachings regarding menstruation in adolescents need to be examined in light of evidence regarding what is "normal." Traditionally, precocious puberty has been defined as any pubertal development occurring before age 8. A large observational cross-sectional study of girls presenting to pediatricians for routine medical care (n = 17,077) evaluated breast and pubic hair development.[1] This study was among the first to suggest that pubertal development appears to be starting earlier than had previously been noted. This study found that nearly half of African American girls had pubertal development before age 8; it is unlikely that all of these girls had significant pathology. Based on this study, it was suggested that new norms for "precocious" puberty be established, with the proposal that it be defined as pubertal development before age 7 in whites and age 6 in African Americans.[2] However, this is still considered controversial, and it should be noted that pathologic causes of precious puberty can still occur in 6- to 7-year-olds; the younger the signs of puberty occur, the more likely a pathologic cause will be found.[3] Regardless, many scholars feel that these new guidelines present a practical, evidence-based approach.[4]

Emerging information about menarche -- onset of the first menstrual period -- from this study and others shows that there are differences between populations, with African American girls in the United States experiencing earlier puberty than Mexican American or white girls.[1,5,6,7,8] While the age of menarche has been declining from the early 1800s until the 1950s, more recently the decline seems to have slowed or stabilized and has only declined slightly since that time.[5,6,7,8,9,10,11,12,13] It has been suggested that the trends toward earlier puberty and menarche are caused by increases in overweight and obesity as reflected by body mass index.[7,8,12,14,15] It has also been suggested that decreases in age at menarche until the mid-1960s resulted from "positive" changes, such as better nutrition, whereas decreases since that time are related to "negative" changes, such as overeating, decreased physical activity, and possibly even chemical pollution.[12] In terms of the significance of earlier pubertal development, breast development before adrenarche (as manifested by pubic hair growth) as a pathway to puberty is associated with a greater proportion of body fat and greater waist circumference and waist/hip ratio; there is also a theorized or possible association with an increased risk for breast cancer or cardiovascular risks later in life.[16]

Delayed pubertal development with the absence of breast development by age 13 is strongly associated with impaired reproductive potential and should prompt an assessment to rule out ovarian failure with abnormal karyotype or other potentially irreversible problems.[17,18] The absence of menstruation by age 15 is also statistically quite uncommon (< 95th to the 98th percentile) and merits investigation.[1,11,19,20,21] This recommendation contrasts to the traditional guideline, which defined primary amenorrhea as lack of menstruation by age 16.



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