Diagnostic Value of Fluorometric Assays in the Evaluation of Precocious Puberty*

Abstract

ABSTRACT To establish normative data and determine the value of fluorometric AutoDELFIA assays (Wallac Oy) in the investigation of precocious puberty, we determined serum levels of LH, FSH, testosterone, and estradiol under basal and GnRH-stimulated conditions in 277 normal subjects at various pubertal stages and in 77 patients with precocious puberty. A substantial overlap was observed in basal and GnRH-stimulated gonadotropin levels in normal individuals of both sexes with pubertal Tanner stages 1 and 2. The 95th percentile of the normal prepubertal population was the cut-off limit between prepubertal and pubertal levels. These limits were 0.6 IU/L in both sexes for basal LH, 9.6 IU/L in boys and 6.9 IU/L in girls for peak LH after GnRH stimulation, 19 ng/dL in boys for basal testosterone, and 13.6 pg/mL in girls for basal estradiol. Basal and peak LH exceeding these limits were considered positive tests for the diagnosis of gonadotropin-dependent precocious puberty. According to these criteria, the sensitivities of basal and peak LH for the latter diagnosis were 71.4% and 100% in boys, and 62.7% and 92.2% in girls. The specificity and positive predicted value were 100% in both sexes for basal and peak LH levels. The negative predicted values for basal and peak LH were 62.5% and 100% in boys, and 40.6% and 76.5% in girls. Basal and GnRH-stimulated FSH levels overlapped among the various pubertal stages in normal subjects and were, in general, not helpful in the differential diagnosis of precocious puberty. In conclusion, basal LH levels were sufficient to establish the diagnosis of gonadotropin-dependent precocious puberty in 71.4% of boys and 62.7% of girls. In the remaining patients, a GnRH stimulation test was still necessary to confirm this diagnosis. Finally, suppressed LH and FSH levels after GnRH stimulation indicate gonadotropin-independent sexual steroid production. (J Clin Endocrinol Metab 84: 3539 -3544, 1999) P RECOCIOUS puberty is due to central activation of the hypothalamic-pituitary-gonadal (HPG) axis [gonadotropin-dependent precocious puberty (GDPP)] or to an abnormal steroid production that does not result from sustained activation of the HPG axis [gonadotropin-independent precocious puberty (GIPP)]. Isolated forms of abnormal pubertal development, such as isolated premature telarche and isolated premature pubarche, are also not associated with central activation of the HPG axis (1, 2). Basal serum levels of LH and FSH determined by traditional RIAs using single polyclonal antibodies overlap substantially and do not distinguish clearly between GDPP and other causes of precocious puberty (3-7). For a more precise diagnosis of GDPP, it is usually necessary to measure serum LH and FSH levels after exogenous GnRH stimulation (1, 8 -12). Recently, new methodologies have been applied to commercial LH and FSH assays. Because of their improved sensitivity, basal gonadotropin levels determined by these assays may provide a better discrimination among the various forms of precocious puberty and thus eliminate the need to perform a GnRH stimulation test. In this study, we used commercial fluorometric AutoDELFIA assays (Wallac Oy, Turku, Finland) to measure basal LH, FSH, testosterone, and estradiol levels as well as GnRH-stimulated concentrations of LH and FSH in normal subjects at various stages of puberty and also in patients with precocious puberty. After analyzing our normative data, we evaluated the diagnostic value of these hormones in distinguishing among the various causes of precocious puberty. Subjects and Methods Subjects The research protocol was approved by the ethical committees of Hospital das Clínicas, Faculdade de Medicina da Universidade de Sao Paulo and Faculdade Federal de Medicina do Triângulo Mineiro, Uberaba (Minas Gerais, Brazil). Written consent to participate in this study was obtained from the subjects or their parents. Two hundred and seventy-seven Brazilian normal subjects (162 males, aged 2-37 yr, and 115 females, aged 2-37 yr) volunteered for this study. None had a history of chronic illness or use of any medication. All had height and weight within 2 sd from the mean for age and sex and a normal physical examination. Pubertal development was evaluated by two endocrinologists according to Tanner's criteria (breast staging in females and testicular size in males) Seventy-seven patients (13 boys, aged 1.2-9.8 yr, and 64 girls, aged 0.9 -8.8 yr) with precocious puberty were recruited for this study. Their height was Ϫ1.0 to ϩ6.5 sd from the mean for age and sex in boys and Ϫ1.7 to ϩ4.2 sd in girls. Bone age according to the method of Greulic