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Assessment of Basal and Gonadotropin-Releasing Hormone-Stimulated Gonadotropins by Immunochemiluminometric and Immunofluorometric Assays in Normal Children

Discipline of Endocrinology and Statistics, Faculdade de Medicina da Universidade Federal do Triângulo Mineiro, 38025-180 Uberaba, Minas Gerais, Brazil

Address all correspondence and requests for reprints to: Elisabete Aparecida Mantovani Rodrigues de Resende, M.D., Federal University of Triângulo Mineiro School of Medicine, S/N Getúlio Guaritá Avenue, 38025-180 Uberaba-MG, Brazil. E-mail: elisabete{at}mednet.com.br.

Context: Recently, new methodologies have been applied to commercial immunofluorometric (IFMA) and immunochemiluminometric (ICMA) LH and FSH assays.

Objective: The objective of the study was to use ICMA to establish basal and GnRH-stimulated LH and FSH reference values in normal subjects of different ages and sexual development, compared with IFMA.

Design and Methods: We established basal and GnRH-stimulated LH and FSH levels of 315 prepubertal and pubertal children (170 males and 145 females) divided into five groups according to Tanner stage. Of these, 106 subjects (59 males and 47 females) were submitted to GnRH test. The prepubertal upper limit of normal for basal LH, determined by the 95th percentiles of the prepubertal population, were 0.2 IU/liter (ICMA) and 0.6 IU/liter (IFMA) in both genders.

Results: No overlap of basal LH levels determined by ICMA was observed between prepubertal and pubertal males, but basal LH determined by IFMA overlapped in 11.8% of subjects. In girls, both methods yielded overlapping values (10.4%, ICMA; and 84.6%, IFMA). The LH peak after GnRH stimulation that defined puberty was 4.1 IU/liter (ICMA) and 3.3 IU/liter (IFMA) in boys and 3.3 IU/liter (ICMA) and 4.2 IU/liter (IFMA) in girls. After GnRH stimulation, values determined by the two methods overlapped in both genders.

Conclusions: We conclude that ICMA is more sensitive and precise than IFMA, permitting differentiation of pubertal and prepubertal stage in boys under basal conditions. However, in girls the overlap of basal values was marked, indicating the need for the GnRH test to establish maturity of the hypothalamus-pituitary-gonadal axis.

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