Immunoreactive LRH (iLRH)-like material has been measured in extracts of urine from normal children and adolescents, adult men and women, and postmenopausal women. The urinary excretion of iLRH-like material was significantly greater in pubertal than in prepubertal subjects and in boys than girls at both stages of sexual maturation [prepubertal males, 3.26 +/- 0.49 ng/24 h (SE; n = 24); pubertal males, 5.94 +/- 1.36 (n = 12); prepubertal females, 1.14 +/- 0.21 (n = 19); pubertal females, 2.85 +/- 0.56 (n = 13)]. In adult males (n = 5) the urinary excretion of iLRH-like material was 7.8 +/- 1.3 ng/24 h, and in adult women in the follicular phase of the menstrual cycle (n = 8) it was 2.9 +/- 0.3. In five postmenopausal women the urinary iLRH-like content was 7.32 +/- 0.92 ng/24 h (P less than 0.01 relative to normal pubertal and adult women). In children the 24-h urinary excretion of iLRH-like material was positively correlated with chronological and bone ages, Tanner stage of genital (male) and breast (female) development, and the urinary excretion of LH and FSH in males. It did not correlate with the urinary excretion of either LH or FSH in females. Carboxymethylcellulose chromatography of extracts of urine from pubertal boys and girls, adult men and women, and postmenopausal women suggested that the iLRH-like material may be the 2-10 fragment of LRH rather than the intact decapeptide.