The other 5 of cases are caused by a disruption of the HPG axis of various

The other 5 of cases are caused by a disruption of

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The other 5% of cases are caused by a disruption of the HPG axis of various etiologies (see Box 25-1).Human gonadal function is partially controlled by luteinizing hormone (LH) and follicle-stimulating hormone (FSH), the release of which is regulated by the pulsatile secretion of hypothalamic gonadotropin-releasing hormone (GnRH).Most recently, the G-protein–coupled receptor 54 (GPR54) has been identified as the gatekeeper gene for activation of the GnRH axis based on loss of function studies in mice and humans. GPR54 is required for the normal function of this axis, and data suggest that the ligand kisspeptin-1 may act as a neurohormonal regulator of the GnRH axis.The mechanisms of childhood inhibition of GnRH release and activation are poorly under- stood but appear to involve feedback inhibition by sex steroids and presumably other central nervous system (CNS) pathways.Given the myriad etiologies contributing to the occurrence of delayed puberty, a thorough evaluation should be conducted that includes physical examination and medical and family history.
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Such evaluation should specifically target known contributors to delayed puberty.Laboratory workup generally consists of x-ray studies for bone age, measurement of thyroid function, serum levels of prolactin and adrenal and gonadal steroids, radioimmunoassay of plasma gonadotropins, and screening forsystemic disorders. Adolescents with high gonadotropin levels require a karyotype, to rule out genetic causes, and those with low levels need skull imaging (lateral skull lm, computed tomography [CT], or magnetic resonance imaging [MRI]) to rule out pituitary or other CNS infiltrate or tumor.2 Although several genes involved in the HPG maturation cascade have been characterized from familial or sporadic cases of primitive isolated hypogonadotropic hypogonadism, many genes regulating puberty onset remain undetermined. Treatment of delayed puberty depends on the cause; the goal of treatment is the development of secondary sex characteristics and fertility, when possible. Insufficient sex hormone secretion can be corrected by hormone replacement therapy, such as testosterone for boys.Idiopathic hypogonadotropic hypogonadism is treated with synthetic GnRH or sex hormone administration, or both, and may be lifelong.Precocious PubertyPrecocious puberty is a rare event in boys, affecting less than 1 in 50,000. Precocious puberty in boys has been redefined as sexual maturation before age 9.One study has noted observed mean ages of beginning male genital and pubic hair growth and early testicular volumes tending toward younger ages than earlier studies have suggested, although this seems to be dependent on race and ethnicity.For instance, black boys are showing significantly earlier mean ages for stages 2 to 4 genital development and stages 2 to 4 pubic hair than white and His- panic boys. All cases of precocious puberty require thorough evaluation. Precocious puberty may be partial, complete, or mixed (heterosexual) types (Box25-2
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