One of the more controversial hypotheses centers on the role of total body weight and body composition on the age of menarche. It is argued that a girl must reach a critical body weight (47.8 kg) before menarche can occur (7). Body fat must increase to 23.5% from the typical 16% of the prepubertal state, which presumably is inﬂuenced by nutritional status (8). This hypothesis is supported by observations that menarche occurs earliest in obese girls, followed by normal-weight girls, then underweight girls, and lastly anorectic girls (Fig. 29.1). The importance of other factors is indicated by observations that menarche is often delayed in morbidly obese girls, those with diabetes, and those who exercise intensely but are of normal body weight and body fat percentage. Girls with precocious puberty may undergo menarche even if they have a low body fat percentage, and other girls show no pubertal development with a body fat percentage of 27% (9). The hypothesis linking menarche to body weight and composition does not always seem valid because menarche is a late event in pubertal development.
The changes associated with puberty occur in an orderly sequence over a definite time frame. Any deviation from this sequence or time frame should be regarded as abnormal.
The pubertal changes, their relationship to one another, and the ages at which they occur are distinctly different in girls than in boys. Although this chapter focuses on girls, changes in boys are considered brieﬂy.
Tanner Stage In girls, pubertal development typically takes place over 4.5 years (Fig. 29.2). The first sign of puberty is accelerated growth, and breast budding is usually the first recognized pubertal change, followed by the appearance of pubic hair, peak growth velocity, and menarche. The stages initially described by Marshall and Tanner are often used to describe breast and pubic hair development (10).
With regard to breast development (Fig. 29.3), Tanner stage 1 refers to the prepubertal state and includes no palpable breast tissue, with the areolae generally less than 2 cm in diameter. The nipples may be inverted, ﬂat, or raised. In Tanner stage 2, breast budding occurs, with a visible and palpable mound of breast tissue. The areolae begin to enlarge, the skin of the areolae thins, and the nipple develops to varying degrees. Tanner stage 3 is reﬂected by further growth and elevation of the entire breast. When the individual is seated and viewed from the side, the nipple is generally at or above the midplane of breast tissue. In most girls, Tanner stage 4 is defined by projection of the areola and papilla above the general breast contour in a secondary mound. Breast development is incomplete until Tanner stage 5, in which the breast is mature in contour and proportion. In most women, the nipple is more pigmented at this stage than earlier in
Figure 29.1 Normal twins at 12 years of age. The heavier twin (weighing 143 lb) is clearly more advanced in puberty than the lighter twin (weighing 87 lb). Anecdotal photographs and data such as these served to provide the basis for the theory that body fat, body mass, and menarche are linked. (From Wilkins L. The diagnosis and treatment of endocrine disorders in childhood and adolescence. 3rd ed. Springfield, IL: Charles C Thomas, 1965, with permission.) development, and Montgomery’s glands are visible around the circumference of the areola. The nipple is generally below the midplane of breast tissue when the woman is seated and viewed from the side. Full breast development usually occurs over 3 to 3.5 years, but it may occur in as little as 2 years or not progress beyond stage 4 until the first pregnancy. Breast size is no indication of breast maturity.