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Chapter 35 PRECOCIOUS PUBERTY
Theodore X. O’Connell
Normal puberty begins between 8 and 14 years of age in girls and between 9 and 14 years of age in boys. Girls begin puberty with breast buds and skeletal growth, followed by the arrival of pubic hair, axillary hair, and menarche. Boys have testicular enlargement followed by the appearance of pubic hair, enlargement of the penis, and spermarche. The age at which pubertal milestones are attained varies among the population studied. In addition, it is influenced by activity level and nutritional status. Girls with low body fat may have a significant delay in menarche (up to a year or longer), whereas obese girls may have earlier onset of puberty.
Precocious puberty is defined as the development of secondary sexual characteristics before the age of 8 years in girls and 9 years in boys. It involves not only early physical changes of puberty, but also linear growth acceleration and acceleration of bone maturation, which leads to early epiphyseal fusion and short adult height.
There are two types of precocious puberty. Central precocious puberty (gonadotropin-releasing hormone [GnRH]-dependent precocious puberty) results from premature activation of the hypothalamic GnRH pulse generator-pituitary gonadotropin-gonadal axis. In peripheral precocious puberty, (GnRH-independent precocious puberty), sex steroid secretion is independent of the GnRH pulse generator. Pathologic causes of puberty are likely if sexual development occurs in very young children or if there is contrasexual development. Peripheral causes are always pathologic and tend to produce an atypical puberty with loss of synchronicity of pubertal milestones.
Central precocious puberty is more common by far in girls than in boys, and in girls it is idiopathic 95% of the time. Boys more commonly (i.e., more than 50%) have an identifiable pathologic peripheral cause for precocious puberty. Therefore, all boys with precocious puberty should undergo detailed investigation. In girls, additional investigation can be based on the clinical impression. Central nervous system (CNS) disorders account for a higher percentage of cases in boys but must also be excluded in girls.
Pubertal variants cause isolated development of one of the secondary sexual characteristics without accelerated skeletal maturation. Occasionally they can progress to precocious puberty.
Simple premature thelarche involves only breast development (unilateral or bilateral), without pubic hair growth, without accelerated bone maturation, and with a normal height outcome. No treatment is required. The disorder is usually self-limited and can resolve spontaneously or persist to normal puberty.
Simple premature adrenarche involves only pubic or axillary hair development, without the other manifestations of puberty. No treatment is required, although late-onset congenital adrenal hyperplasia should be ruled out with a measurement of the serum 17α-hydroxyprogesterone level. There is an increased incidence of simple premature adrenarche in patients with CNS abnormalities.
Unilateral or bilateral gynecomastia may occur in boys as puberty begins. In fact, this is a nearly universal finding among boys in middle to late puberty. It usually resolves within 2 years. Pathologic gynecomastia occurs in Klinefelter’s syndrome, prolactin-secreting adenomata, and as a result of drugs such as marijuana and phenothiazines.
Patients with precocious puberty and pubertal variants require an initial bone age as a baseline. In precocious puberty, the bone age is usually accelerated more than two standard deviations above the chronological age. In pubertal variants, the bone age should be within two standard deviations of the chronological age. The bone age should be obtained at periodic intervals to determine whether pubertal variants have progressed to precocious puberty. The bone age is also used to monitor the effectiveness of therapy. Additional evaluation of precocious puberty is outlined below.
Androgens
Estrogens
GnRH-Dependent Precocious Puberty
CNS tumors
Instant Work-ups A Clinical Guide to Pediatrics
