Comparison of estimates of gonadotropin levels by isolated blood samples, integrated blood concentrations, and timed urinary fractions.

Gonadotropin levels in isolated blood samples, integrated plasma concentrations (IC), and timed urinary collections have been compared in 5 males with delayed puberty and 7 normal adult males. There was a significant correlation between urinary levels in 24-h collection and those in each of four shorter timed collections for both LH and FSH. Similarly, 24-h integrated plasma concentration and 4-h (0800--1200 h) integrated plasma concentration obtained on 10 additional subjects showed significant correlation. The 4-h integrated plasma concentrations correlated with single blood samples or the mean of three samples obtained at 0800, 1200, and 1600 h. These 4-h plasma samples also correlated significantly with all urine collections for FSH but only with the 2200--0800 h urine collection for LH. The study suggests that LH and FSH levels in urine samples collected over several hours correlate with 24-h urinary excretion and that levels in single blood samples estimate the 24-h plasma integrated concentration.