A clinically useful method for detecting gonadotropins in children: assessment of luteinizing hormone and follicle-stimulating hormone from urine as an alternative to serum by ultrasensitive time-resolved immunofluorometric assays.

To study the feasibility of noninvasive sampling in pediatric patients, we examined the concentrations of LH and FSH in paired serum and urine samples from 65 children (age 0-15 y) with highly sensitive time-resolved immunofluorometric assays. The detection limits of the assays were 0.015 IU/L for LH and 0.018 IU/L for FSH. These sensitivity levels allowed quantification of the low prepubertal LH and FSH concentrations. The correlation between serum and urine gonadotropin values was very good (r = 0.751, p < 0.001 for FSH; and r = 0.720, p < 0.001 for LH), and the urine and serum concentrations were very similar. Correction of urinary gonadotropin concentrations for changes in urinary flow by standard methods using density [concentration x (0.02/density-1)] or creatinine (concentration/creatinine) did not improve the correlation. Therefore, measurement of urinary gonadotropins without correction can simply be used in the pediatric outpatient setting as a noninvasive alternative to serum determinations.