How Long Does a Girl Continue to Grow After She Starts Her Period
West J Med. 2000 Mar; 172(3): 182–185.
Topics in Review
Myths and variations in normal pubertal development
Jon M Nakamoto
1 Department of Pediatrics and Endocrinology Mattel Children's Hospital at UCLA 22-315 MDCC 10833 Le Conte Ave Los Angeles, CA 90095-1752
Myths about puberty are common. These misconceptions create needless anxiety, for example, in parents who confuse the isolated development of pubic hair or breasts with true sexual maturation. Even healthcare providers are not immune: some may be unaware of recent data suggesting that in healthy girls puberty may begin earlier than the textbook age of 8 years and others may mistakenly inform parents that only a couple of inches of growth remain for their 10-year-old daughter who has started menstruating. This article discusses common myths that surround the normal variations in pubertal development.
Summary points
METHODS
Topics chosen for discussion in this article reflect the most common misconceptions about pubertal development encountered in my practice. The evidence presented was obtained from published articles and reviews identified through MEDLINE searches, as well as practice guidelines derived from recent subspecialty meetings, and pediatric endocrinology discussion groups on the Internet.
BENIGN PREMATURE ADRENARCHE
Myth: pubic hair signals the onset of puberty
The reality is that without breast or testicular enlargement, pubic hair (pubarche) and body odor indicate increasing adrenal secretion of weak androgens (adrenarche) rather than activation of the hypothalamic-pituitary-gonadal unit (true puberty). Before 1997, premature adrenarche was defined as pubic hair developing in girls younger than 8 years old and boys younger than 9 years. However, the results of a large, cross-sectional study suggest that the development of pubic hair may be normal in white girls as young as 7 years and in African American girls as young as 6 years.1
Although the definition of normal puberty, as compared with premature, remains in flux, unquestionably early pubarche is likely to be benign if it meets the criteria in the box. If these criteria are met, then for most children a diagnostic workup can be limited to continued observation. Some physicians order an x-ray film to check that the skeletal age of the child is no more than 2.5 standard deviations (typically about 2 years) above the chronologic age. An abdominal ultrasound scan or blood tests for dehydroepiandrosterone sulfate, 17-hydroxyprogesterone, and testosterone are rarely needed.
Characteristics of benign premature adrenarche
BENIGN PREMATURE THELARCHE
Myth: breast development signals the onset of puberty
In reality breast enlargement occurring in isolation in girls younger than 6 years or in infants is more likely to represent benign premature thelarche than true precocious puberty. The criteria in the box may be useful in making this differential diagnosis. In cases in which true precocious puberty is suspected, sensitive methods of diagnosis include pelvic ultrasound scanning (uterine enlargement confirms that there is an increased effect of estrogens and bilateral ovarian enlargement strongly suggests activation of the central hypothalamic-pituitary axis) and ultrasensitive immunochemoluminometric assays of luteinizing hormone.2
Characteristics of benign premature thelarche
EARLY NORMAL PUBERTY
Myth: girls are starting puberty earlier
The reality is that this may be partially true: although the average age at menarche (12.8 years) has not fallen much in the past 60 years, more recent data suggest that the lower age limit for normal thelarche or pubertal onset is below the threshold of 8 years that is cited in many texts.1 , 3 Recently published guidelines suggest that extensive evaluation is not routinely needed in healthy girls with thelarche or puberty occurring as early as age 7 in white girls or 6 in African American girls.4 However, there is disagreement over whether thelarche or puberty occurring in 6 and 7 year olds is normal, and most pediatric endocrinologists still recommend close evaluation and follow up of girls who start thelarche and the progression of puberty at this age. For boys, the lack of new clinical data and the greater chance of disease lead to a continuing recommendation that boys younger than 9 years who have penile enlargement, scrotal thinning, and accelerated growth should be formally evaluated.
Possible reasons for the finding of earlier thelarche or puberty include ascertainment bias; exposure of children to environmental estrogens from plastics, foods, and pesticides; improvements in socioeconomic status; or earlier maturation caused by the rise in the average body weight of children. This last possibility raises interesting questions about the relation between body weight and pubertal onset. For some species the relation is direct: cattle ranchers know that sexual maturity in a heifer depends more on reaching a critical weight than a specific age. For humans, mild obesity is associated with a slight advancement in skeletal age and earlier onset of puberty.5 Theories about the action of the hormone leptin and its role in the regulation of body weight and puberty and fertility are evolving rapidly and have implications for conditions such as precocious or delayed puberty, anorexia nervosa, obesity, and anovulation.6
Myth: menarche means the end of growth is near
The reality is that the average gain in height after menarche is about 7 cm (3 inches), and it is even greater for girls who menstruate on the early side of normal. Follow-up data from the Fels Longitudinal Study show that girls who start menstruating at age 10 grow, on average, 10 cm (4 inches), while those in whom menarche is delayed until age 15 grow, on average, 5 cm (2 inches).7 Additional reassurance is provided by data suggesting that earlier thelarche is associated with a increased interval before menarche: for example, an 8- or 9-year-old girl who has just started developing breasts will have an average time to menarche that is closer to 3 years than 2.8 The combination of a longer time before menarche and greater height gain after the start of menstruation may explain why girls who start puberty at about 6 to 8 years old do not end up short as adults. Conversely, the lesser gain in height after menarche and shorter interval between thelarche and menarche in girls with pubertal delay may explain why the pharmacologic delay of puberty (using depot gonadotropin-releasing hormone agonist preparations) has inconsistent and limited effects on increasing their final height.9
CONSTITUTIONAL DELAY OF GROWTH AND PUBERTY
Myth: dropping down to a lower centile on a height chart always signifies a pathologic condition
The reality is that in many cases an adolescent who is falling off the growth curve will prove to be healthy but have a constitutional delay of growth and puberty. These late bloomers typically move to a lower height centile sometime before the age of 3 years, then remain on the same height centile throughout most of their childhood. At around 12 to 14 years of age for boys (10 to 12 years for girls), which is the typical period of concern, they again cross downward to a lower height centile (figure), due to the delayed onset of their pubertal growth spurt relative to their peers.
Typical height pattern (plotted on a standard growth chart) for a boy with constitutional delay of growth and puberty. Note the decrease in height centile starting around age 12 years
Unfortunately, there is often no certain method to distinguish healthy adolescents who are late bloomers from the rarer few with true disease. A comprehensive history and physical examination, emphasizing the detection of dysmorphism or diseases of the central nervous system and gastrointestinal system, is mandatory. Careful interpretation of a bone-age x-ray film, tempered by an understanding of its limitations, allows for an estimate of the adolescent's final adult height and comparison with the calculated mid-parental target height. For the experienced physician with proper tools (for example, a Prader orchiometer to measure testicular size), accurate assessment of pubertal development provides as much information as the bone-age x-ray film: the typical male adolescent with no delay in skeletal age has an onset of testicular enlargement (>3 ml volume or >2.5 cm [>1 inch] in length) at 11.5 years of age, increasing to 12 ml (corresponding to peak growth velocity) by 14 years of age.10 The onset of breast development in a girl suggests a skeletal age of 10 or 11 years.
Laboratory investigations that are useful in slowly growing adolescents
At this point, physicians may take divergent approaches, with some sending the adolescent for laboratory investigations immediately and others preferring to observe height velocity (correlated with skeletal age rather than chronologic age) before embarking on more extensive evaluation. Some laboratory investigations that are useful in evaluating these adolescents are shown in the box.
Myth: testosterone treatment of boys with constitutional delay reduces final adult height
In reality, in boys with constitutional delay and a skeletal age older than 10 years, low-dose testosterone (typically 50 mg monthly intramuscularly for 3-12 months) accelerates growth (often doubling height velocity) and the development of secondary sexual characteristics without decreasing their final adult height.11 The onset of the growth spurt may occur up to a year earlier than without treatment. Low doses of oral anabolic steroids (up to 2.5 mg/day), such as oxandrolone or fluoxymesterone, also increase growth without having negative effects on final height but are used less often because of their potential hepatotoxicity and less satisfying effects on secondary sexual characteristics.12 , 13 At these low doses, testicular enlargement should continue, providing reassurance that the boy has simple constitutional delay and not a more permanent deficit of hypothalamic-pituitary function (hypogonadotropic hypogonadism).14
At higher doses (particularly those used off-label by athletes), androgens will decrease adult height by promoting maturation of epiphyseal growth plates more rapidly than linear growth. It is critical to clarify the differences between carefully monitored, low-dose testosterone treatment of constitutional delay and anabolic steroid abuse used to gain unfair athletic advantage.
CONCLUSIONS
Adolescents and younger children with benign variants of normal pubertal development—such as premature adrenarche or thelarche, early normal puberty, and constitutional delay—are common in pediatric practice. Recognizing that such variants are normal is an important skill. By refuting the most common myths about these variants and other aspects of normal puberty, providers can greatly relieve the anxiety of parents and children and avoid making unnecessary referrals.
Notes
Funding: None
Competing interests: None declared
References
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Articles from The Western Journal of Medicine are provided here courtesy of BMJ Publishing Group
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1070801/
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