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(Pediatrics in Review. 2006;27:373-381.)
© 2006 American Academy of Pediatrics
Objectives |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Introduction |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Case History |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Definitions |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Thelarche (th-lar’k), the onset of female breast development, is characterized by tender nodules of firm tissue centered on the areolae, which usually are appreciable by palpation before they are by visual inspection. In overweight girls, palpation is essential to distinguish sex steroid-dependent breast (firm, nodular, and possibly tender) from adipose tissue (soft, homogeneous, and nontender). Adrenarche (ad‘ren-ar’k) is the onset of androgen-dependent signs of puberty (pubic hair, acne, and adult body odor). In females, adrenarche is the result of adrenocortical activity. In males, either adrenal or gonadal maturation can prompt adrenarche. Some sources refer to adrenarche as pubarche (pu-bar’k). Menarche (m-nar’k) is the onset of menstruation.
Epidemiology |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Table 1. Pubertal Milestones
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Male puberty is more difficult to assess in research settings than is female puberty. Using increased testicular size to mark pubertal onset, most studies report a mean age of pubertal onset near 11.5 years in males (Table 1). Adrenarche typically is seen around the 12th birthday in boys, with African-Americans having a slightly lower mean age of onset compared with Caucasians. Males take an average of 4 years to progress through puberty.
Genetic and environmental factors influence the onset of puberty. Improved nutrition is considered the primary reason for the secular decline in pubertal age. Furthermore, childhood obesity has been associated in longitudinal studies with early puberty in girls. However, there are other important determinants of puberty. Precocious puberty was noted among children who had been adopted recently from a developing to a developed county. This was seen more frequently among girls than boys and could not be explained entirely by changes in nutrition, body weight, or body fat. Birth date uncertainty accounts for a portion of the children believed to have early pubertal development. Other environmental determinants, however, may include stress, climate and light cycles, and chemical exposures.
Environmental determinants of puberty are important because such exposures can be changed when necessary. It appears likely, however, that among healthy children in developed countries, genetic influences on puberty outweigh the environmental influences by a factor of about three. Genetic determinants of pubertal onset were demonstrated in traditional twin studies in which the correlation coefficient between age of pubertal onset in monozygotic twins exceeded that in dizygotic twins. As expected, the correlation in dizygotic twins was equal to that seen in singleton siblings. Currently, candidate puberty control genes include steroid hormone receptors, biosynthetic and catabolic enzymes, and transcription factors.
Pathogenesis |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Table 2. Differential Diagnosis of Precocious Puberty
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Control of Normal Pubertal Onset |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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The hypothalamic-pituitary-gonadal axis is functional by 20 weeks’ gestation and remains active throughout much of the remaining gestation. A brief spurt of central pubertal axis activity on the first day after birth is followed by a period of quiescence. During the first postnatal month, GnRH pulses recur spontaneously. In males, this infantile central activity reduces to near prepubertal levels by about 3 to 6 months of age. Gonadotropin secretion, particularly of FSH, may persist in females until 18 months of age. During the subsequent prepubertal period, gonadotropin secretion is minimal and cannot be stimulated by a single intravenous GnRH infusion. As puberty begins, gonadotropins are released from the pituitary gland in a pulsatile fashion, particularly at night. With increased gonadotropin release comes the ability of exogenous GnRH to stimulate release of FSH and later both LH and FSH.
Normal onset of puberty is determined by multiple incompletely understood intracerebral processes. In a simplified model, gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter that inhibits GnRH secretion. In contrast, glutamatergic neurotransmission stimulates GnRH production. Changes in the balance of these signals trigger puberty. It is not yet known whether GABA-mediated neurotransmission is reduced at pubertal onset, allowing increased glutamatergic signals, or vice versa. The results of recent investigations of the ligand-receptor pair of Kisspeptin-1 and GPR54 need to be incorporated into the neurochemical model of puberty. Kisspeptin-1, released by forebrain neurons, becomes an efficient activator of GPR54 on GnRH-secreting neurons at the time of puberty, and this activation is associated with GnRH release. Much, however, remains to be learned. For example, GnRH production is influenced by neuropeptides, such as neuropeptide Y and norepinephrine. Furthermore, neurocommunications exist between astroglial cells and GnRH-producing neurons.
Applying Physiology to Precocious Puberty |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Gonadotropin-independent sexual precocity can arise from a variety of anatomic or functional lesions that are discussed only briefly here. Benign or malignant tumors of the adrenal cortex or gonad can produce sex steroids autonomously. Follicular ovarian cysts may cause transient or persistent signs of puberty. Usually, estrogen-dependent effects, such as breast development, maturation of the vaginal mucosal, or vaginal bleeding, predominate.
Biosynthetic defects of glucocorticoids causing congenital adrenal hyperplasia (CAH) and glucocorticoid resistance are conditions that raise ACTH-induced production of adrenocortical androgens (Fig. 4) and cause premature adrenarche and rapid skeletal growth in males and females. Clitoromegaly can occur in girls, but normal phallus size is seen in males. Central precocious puberty also can arise in children who have CAH if their bone age advances to the age of normal pubertal onset.
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Prolonged hypothyroidism is a curious cause of precocious puberty that may result from gonadotropin-like action of thyroid-stimulating hormone (TSH) or activation of gonadotropin receptors by TSH. TSH is another heterodimeric glycoprotein that shares the alpha chain of gonadotropins. Hyperprolactinemia, induced in hypothyroidism by high concentrations of thyrotropin-releasing hormone, may sensitize the ovary to gonadotropins.
A number of genetic lesions in hormone synthetic enzymes, receptors, and postreceptor signals cause abnormal sex steroid production. Excess aromatase activity, converting androgens to estrogens, has been reported to cause premature thelarche in girls and gynecomastia in boys. Mutations of the LH receptor can result in unbridled Leydig cell activity and the syndrome of familial male-limited precocious puberty (testotoxicosis). Constitutive postreceptor signals from mutated stimulatory G-protein complexes cause the McCune-Albright syndrome (precocious puberty, café au lait macules, polyostotic fibrous dysplasia).
Sources of exogenous sex steroids can include oral contraceptives, skin creams, meat from hormone-treated animals, plant phytoestrogens, and anabolic steroids. Unless a hormone preparation contains both androgens and estrogens, exogenous steroid exposure usually causes a picture of incomplete puberty.
Other syndromes of incomplete puberty include benign premature thelarche and adrenarche. In the former condition, unilateral or bilateral breast development is observed with minimal or no other clinically apparent estrogen effects. About 60% of cases are identified between 6 to 24 months of age, and diagnosis after 4 years is unusual. Normal, rather than accelerated, growth velocity and minimal progression of breast development distinguish this condition from those that require treatment. Importantly, about 10% of girls who have typical benign idiopathic thelarche eventually develop true central precocious puberty and require treatment. Children who have premature adrenarche have isolated signs of adrenal sex steroid production (pubic hair, acne, body odor) that progress slowly and are associated with normal growth velocity and a height commensurate with their skeletal maturation (bone age). Children who experience intrauterine growth restriction are at risk for this condition. Although treatment of idiopathic premature adrenarche is not recommended in children, some 20% of affected girls develop clinically significant ovarian hyperandrogenism as adults.
About 60% of cases of premature thelarche are identified between 6 and 24 months of age. ...
Clinical Evaluation |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Physical Examination
The linear growth spurt is a feature of early puberty in females. Maturation of the vaginal mucosa is a sensitive indicator of estrogen activity that may appear before breast tissue can be appreciated. Clitoromegaly, a sign of abnormally high androgen levels, is never part of normal female puberty. The first signs of male puberty are thinning of the scrotum and enlargement of the testes beyond 3 mL. The Prader orchidometer is used to determine testicular volume, although testicle length standards also are available. Growth of the phallus and pubic hair follow. The skeletal growth spurt usually peaks at SMR 4 in males. Dental development provides the examiner a simple method of approximating bone age in both females and males.
Much can be learned from the testicular examinaton of boys who have early puberty. Testicle volumes greater than 3 mL bilaterally usually indicate gonadotropin action. Lesions causing premature testicular enlargement, however, are not always neurologic. Owing to the selective stimulation of Leydig cells by hCG, testes that have been exposed to tumor-derived hCG exceed the size of prepubertal gonads, but are smaller than those seen in children who have true central precocity. Familial male-limited precocious puberty causes bilateral testicular enlargement and usually is suspected because of the young age of onset and a family history of sexual precocity in males. Testicular tumors typically are unilateral, although bilateral adrenal rest in boys who have poorly controlled CAH is a cause of bilateral testicular enlargement. Testes of prepubertal size in a boy who has isosexual precocious puberty usually indicates that androgen is arising from either the adrenal gland or an exogenous source.
Laboratory Evaluation
The diagnostic laboratory evaluation of children who experience early puberty should confirm the source of hormone. The normal ranges of pubertal hormones vary with the stage of pubertal development. When interpreting hormone results, it is important, therefore, to determine whether a result is consistent with the stage of pubertal development, rather than with the child’s chronologic age. For
a child whose hepatic function is normal, the serum
dehydroepiandrosterone sulfate (DHEA-S) concentration provides an
estimate of adrenocortical sex steroid production. Values elevated
beyond that expected for pubertal stage suggest adrenal pathology (eg,
CAH, adrenal tumor). Biosynthetic defects of adrenocortical steroids are identified best by high concentrations of the substrate for the enzyme that is deficient. For example, 21-hydroxylase deficiency is diagnosed by determining the serum 17-hydroxyprogesterone concentration (Fig. 4). Random measures of testosterone or estradiol are helpful for detecting gonadal steroid production. Advanced bone age, especially if it has progressed beyond the height age, serves as a nonspecific biomarker of abnormal sex steroid production. Among children who have idiopathic central precocious puberty, bone age helps determine whether treatment to stop additional development will be of value.
Because normal pituitary gland secretion of gonadotropins is pulsatile, randomly obtained serum samples do not reliably contain enough LH and FSH to permit traditional assays to diagnose the onset of puberty. Although today’s most sensitive gonadotropin assays may be able to distinguish between basal gonadotropin levels of prepubertal and pubertal children, most commercial gonadotropin assays do not. Therefore, definitive demonstration of an activated central axis driving early puberty usually requires stimulation testing with exogenous GnRH. A single injection of GnRH will not increase the serum gonadotropin concentrations in children who have a quiescent central pubertal axis (ie, prepubertal or precocious puberty from noncentral dysfunction). Once the hypothalamic-pituitary axis has become active, however, the injection causes a rise of FSH in early puberty, and increased LH release is the most specific indicator of central puberty. The demonstration of central precocious puberty by GnRH testing should prompt a magnetic resonance study of the brain with high-resolution imaging of the hypothalamus and pituitary gland.
Management |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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The management of autonomous gonadal steroid secretion in McCune-Albright syndrome and familial male-limited precocious puberty can be difficult. Medications to block: a) steroid production (eg, ketoconazole), b) 5-alpha reductase activity (eg, finasteride), c) steroid receptors (eg, flutamide, spironolactone), and d) aromatase activity (eg, testolactone, anastrozole) have been suggested, but formal trials are limited.
The demonstration of central precocious puberty should prompt a magnetic resonance study of the brain. ...
Children who have severe brain dysfunction and central precocious puberty present special ethical concerns. GnRH therapy may reduce behavioral problems and provide effective contraception. Therefore, it may be tempting to offer this treatment to children who have limited cognitive abilities and multiple special care needs. Reduced bone mineral density, eunuchoid growth, and ethical considerations arising from "chemical castration," however, are important disadvantages that must be considered.
Adrenocortical steroid production of androgens can be controlled with glucocorticoid replacement in patients who have CAH. This treatment, however, may be ill advised for children who have late-onset forms of 21-hydroxylase deficiency and who are able to mount a normal glucocorticoid response to stress and predicted to have a normal final height. The risk of iatrogenic adrenocortical suppression may outweigh any benefits that treated children may accrue from chronic glucocorticoid therapy.
Prognosis |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Summary |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Footnotes |
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Dr Muir did not disclose any financial relationships relevant to this article.
Suggested Reading |
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Top Objectives Introduction Case History Definitions Epidemiology Pathogenesis Control of Normal Pubertal... Applying Physiology to... Clinical Evaluation Management Prognosis Summary Suggested Reading |
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Denburg MR, Silfen ME, Manibo AM, et al. Insulin sensitivity and the insulin-like growth factor system in prepubertal boys with premature adrenarche. J Clin Endocrionol Metab. 2002;87 :5704 –5709
Dungan
HM, Clifton DK, Steiner RA. Kisspeptin neurons as central processors in
the regulation of gonadotropin-releasing hormone secretion.
Endocrinology. 2006;147
:1154
–1158
Kaplowitz PB, Oberfield SE. Reexamination of the age limit for defining when puberty is precocious
in girls in the United States: implications for evaluation and
treatment. Drug and Therapeutics and Executive Committees of the Lawson
Wilkins Pediatric Endocrine Society.
Pediatrics. 1999;104
:936
–941
Klein KO, Barnes KM, Jones JV, et al. Increased final height in precocious puberty after long-term treatment with LHRH agonists: the National Institutes of Health experience.
J Clin Endocrinol Metab. 2001;86
:4711
–4716
Marshall WA, Tanner JM. Variations in pattern of pubertal changes in girls.
Arch Dis Child. 1969;44
:291
–303
Marshall WA, Tanner JM. Variations in pattern of pubertal changes in boys.
Arch Dis Child. 1970;45
:13
–23
Midyett LK, Moore WV, Jacobson JD. Are pubertal changes in girls before age 8 benign?
Pediatrics. 2003;111
:47
–51
Parent A-S, Teilmann G, Juul A, et al. The timing of normal puberty and the age limits of sexual precocity: variations around the world, secular trends, and changes after migration.
Endocrine Rev. 2003;24
:668
–693
Pucarelli I, Segni M, Ortore M, et al. Effects of combined gonadotropin-releasing hormone agonist and growth hormone therapy on adult height in precocious puberty: a further contribution. J Pediatr Endocrinol Metab. 2003;16 :1005 –1010[Medline]
Terasawa EI, Fernandez DL. Neurobiological mechanisms of the onset of puberty in primates.
Endocrine Rev. 2001;22
:111
–151
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