General Medical Information

Normal Pubertal Development

Sander S. Shapiro and Joel S. Krasnow

Puberty refers to those developmental processes initiated in late childhood that culminate in adult reproductive competence. It involves a group of qualitative changes that depart from the generalized somatic growth processes that are dominant throughout childhood. Attainment of puberty is associated with profound hormonal alterations, the acquisition of secondary sexual characteristics, a short-lived increase in longitudinal growth rate, and numerous psychosocial changes. None of these events, however, either alone or in concert, absolutely signifies that an individual has established a reproductive capacity. Thus, puberty is a rather general term that connotes the transition period between childhood and adulthood.

The age at which the somatic changes associated with puberty occur is highly variable. A majority of North American females initiate pubertal alterations between 8 and 13 years of age. Their male counterparts initiate analogous pubertal development at 9 to 14 years of age. Between 1% and 2% of the population will start their transition outside of this range and thereby invite evaluation for either precocious or delayed puberty.

The first somatic change that occurs in females is either the beginning of breast (thelarche) or pubic hair (pubarche) development. The onset of both thelarche and pubarche are variable, with a mean of 10.9 and 11.2 years, respectively, for North American females. Tanner described five stages of breast and pubic hair development, but seldom documented, change is the onset of the “adolescent growth spurt.” This change in growth velocity has a mean onset of 9.6 years. The peak height velocity (PHV) occurs almost 2.5 years later and precedes the onset of menses (mean age 12.7 years). The interval between onset of breast development and menarche is 2.3 ± 1.0 years and is independent of the age at which thelarche occurs. However, a wider temporal range exists for the onset, duration, and completion of these transforming events. Within the spectrum of normal pubertal development, it is possible to see physical changes as much as 5 years before menarche. It also is possible for the sequence of physical changes to vary considerably from the order discussed. Such variability can lead to expressions of concern on the part of adolescents and their parents. Therefore, it is helpful for medical practitioners to have a firm sense of the wide temporal range of pubertal events and an understanding of when to initiate an evaluation for those who present outside popularly perceived norms.

The average age of pubertal onset, as well as the age of first menses (menarche), has declined steadily over the last century in this country and throughout the industrialized world. Most recently, however, this trend has leveled off and may even be going in the opposite direction. At present, the average age of menarche is about 12.7 years. This has been attributed to improved nutritional and general health conditions, as well as to altered lifestyles. In isolated nomadic tribes, where living conditions and socialization practices have not changed significantly during recent times, the trend toward earlier menarche is not found. In addition, strenuous physical activity, decreased body fat content, chronic disease, and malnutrition are all associated with delayed puberty. Conversely, females with moderately increased fat content tend to experience menarche at an earlier age. Thus, geographic, nutritional, and sociologically determined factors may affect the time at which puberty begins and its rate of progression. Furthermore, daughters frequently experience menarche at an age that is close to their mother’s menarcheal age, suggesting that genetic factors may contribute to the timing of pubertal events.