ESPE Abstracts

Objectives: We aimed to study the daily variation in first morning urinary total luteinizing hormone (U-LH) determination and validate it as a noninvasive method for analyzing age- and pubertal stage-related changes in LH immunoreactivity (LH-ir) levels to predict imminent onset of central puberty.

Methods: We determined three consecutive first morning total U-LH along with spot serum LH and follicle-stimulating hormone concentrations in 354 children (160 boys aged 2.8–17.8 yr and 194 girls aged 2.6-18.0 yr) with known pubertal stages. The samples were analyzed using an immunofluorometric assay (Delfia, PerkinElmer, Finland). The net day-to-day variation (net CV%) in U-LH-ir levels was calculated by subtracting the inter-assay CV% of the assay reported by the manufacturer from the gross inter-assay CV% calculated from three consecutive samples. U-LH-ir levels were categorized as prepubertal, peripubertal (highly likely pubertal), and pubertal based on the cutoffs established in our recent study.

Results: On average, the gross and net inter-assay CV% values for different U-LH concentrations measured on three consecutive mornings were 37.6% and 32.7%, respectively. Despite this level of day-to-day variation, only 3.6% of the test results for boys and 4.9% for girls were inconsistent in classifying total U-LH-ir levels as prepubertal, peripubertal, or pubertal. First morning total U-LH-ir levels confirmed the sex-independent timing of central activation of the hypothalamo-pituitary-gonadal hormone axis. Further, our findings confirmed that the onset of pubertal gonadotropin secretion in boys occurs already at a testicular volume of 1 to 2 mL, well before clear clinical signs of puberty.

Conclusion: A single first morning total U-LH measurement appears to be a valid clinical test for classifying children or adolescents into prepubertal, peripubertal, and pubertal groups. This study validates the recently reported finding that the timing of central puberty onset is sex-independent. The duration between the initial activation of gonadotropin secretion and the first clinical signs of puberty was longer in boys than in girls.