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Am Fam Physician. 2000;62(6):1406-1410

Myths about puberty can cause unnecessary anxiety in parents. Nakamoto discusses six common misconceptions about pubertal development.

Myth number 1 is that development of pubic hair signals the onset of puberty. Without breast or testicular enlargement, growth of pubic hair (pubarche) and the presence of body odor simply indicate increased adrenal secretion of weak androgens (Table 1). Such changes do not signify activation of the hypothalamic-pituitary-gonadal unit (true puberty). Recent cross-sectional studies suggest that the development of pubic hair may be a normal variation in white girls as young as seven years and in black girls as young as six years. This finding alters the previous definition of premature adrenarche, which has been defined as the growth of pubic hair in girls younger than eight years and in boys younger than nine years.

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Myth number 2 is that breast development signals the onset of puberty in girls. Breast enlargement in girls younger than six years is more likely to represent benign premature the-larche than true precocious puberty (Table 2). If precocious puberty is suspected, methods of diagnosis include pelvic ultrasound examination to document uterine enlargement and ultrasensitive assays of luteinizing hormone.

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Myth number 3 is that puberty in girls now begins earlier than it did in the past. The average age at menarche (12.8 years) has not fallen in the past 60 years, but the lower age limit for normal thelarche or pubertal onset is now generally considered to be below the eight years of age cited in most texts. Most pediatric endocrinologists, however, still recommend evaluation and follow-up of girls who start thelarche at six to seven years of age. Evaluation is also recommended when boys younger than nine years show signs of puberty, such as penile enlargement, scrotal thinning and accelerated growth. Possible reasons for earlier thelarche or puberty include increased exposure to environmental estrogens, improvement in socioeconomic status or an increased average body weight in children.

Myth number 4 is that menarche signals that the end of growth is near. The reality is that the average gain in height after menarche is about 7 cm (3 inches). The gain in height is even greater (4 inches or more) in girls who menstruate early.

Myth number 5 is that a drop to a lower centile on a height chart always signifies a pathologic condition in an adolescent. In reality, such an adolescent is usually healthy but has a constitutional delay of growth and puberty. Adolescents with this pattern of growth typically drop downward to a lower height centile at 12 to 14 years of age for boys and 10 to 12 years of age for girls. There often is no way to discern between healthy adolescents who are late bloomers and the rare few with a disease. A history and physical examination are important for detecting a disorder that might be responsible for slowed growth. Bone-age radiographs may allow for an estimate of the adolescent's final height.

Myth number 6 is that final height will be shorter if testosterone is administered to boys with constitutional delay. In reality, low-dose testosterone (typically 50 mg monthly, given intramuscularly for three to 12 months) accelerates growth and the development of secondary sex characteristics without impeding adult height. Low doses of anabolic steroids may achieve the same goal but are less commonly used because of potential hepatotoxicity and less satisfying effects on secondary sexual characteristics. At higher dosages, androgens lead to a shorter adult height by promoting maturation of epiphyseal growth plates more rapidly than linear growth. Of course, gonadal enlargement may not continue at the low dosages if the boy has a more permanent deficit of hypothalamic-pituitary function (hypogonadotropic hypogonadism).

The author concludes that benign variants of normal pubertal development are common. The anxiety of parents and children can be relieved by recognizing such patterns of development, thereby avoiding unnecessary testing or referral to subspecialists.

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