Pathogenesis and management of abnormal puberty.

Abstract

In the prepubertal child, the hypothalamic-pituitary-gonadal (H-P-G) axis is functional and extremely sensitive to negative feedback inhibition by low circulating levels of sex steroids. This feedback system may be under the control of unknown CNS inhibitory mechanisms. Clinical signs of puberty are preceded by increased pulsatile secretion of hypothalamic gonadotropin-releasing hormone (GnRH) followed by increased pituitary responsiveness to GnRH. Gonadotropin secretion, particularly LH, increases in both sexes, especially during sleep, resulting in gonadal stimulation, secretion of sex steroids, and progressive physical maturation. When any phase of the H-P-G axis malfunctions, abnormal puberty can result. Abnormal puberty may be precocious or delayed. When puberty is precocious it may be isosexual or heterosexual, complete or partial, intermittent (unsustained), or progressive. True (central) precocious puberty is usually progressive, and hormonally reflective of normal puberty, although occurring at an earlier age, whereas intermittent or unsustained precocious puberty usually is associated with immature patterns of gonadotropin secretion, or with complete gonadotropin suppression as in precocious pseudopuberty (ovarian or adrenal tumors). Cranial axial tomography, gonadotropin response to GnRH, and pelvic ultrasound in girls are useful tools to aid in the differential diagnosis of these conditions. Intermittent, or unsustained, puberty in girls is usually self-limited, requiring no medical or surgical intervention. True progressive central precocity may now be managed with GnRH analogues, which effectively arrest pubertal changes as well as slow rapid linear growth and skeletal maturation. Although a maturation lag usually explains most patterns of delayed puberty, it is often challenging to exclude other conditions that may contribute to slow pubertal progression, such as chronic illness, excessive exercise, emotional stress, anorexia, or drug use. Elevated serum gonadotropin levels direct further evaluation toward etiologies of gonadal failure, including gonadal dysgenesis, Klinefelter syndrome, and chemotherapy/irradiation damage. Both low gonadotropins and absence of or immature gonadotropin response to GnRH administration after a bone age of 11 years in girls and 13 years in boys point toward hypopituitarism or isolated hypogonadotropic hypogonadism. Management with administration of gradually incremented amounts of sex steroids at an appropriate psychologic age usually leads to enhanced linear growth, physical maturation, and improved self-esteem.