The MCR of biosynthetic human GH was studied in 12 prepubertal children, 9 adult women, and 13 adult men. Subjects received a constant infusion of biosynthetic GH, and clearance was calculated by dividing the infusion rates by steady state serum concentrations of GH. We found that adult men have a significantly more rapid MCR of human GH than women (125.2 +/- 7.6 mL/min.m2 in men; 89.4 +/- 7.7 mL/min.m2 in women) and that both men and women have a significantly more rapid MCR of human GH than prepubertal children (66.8 +/- 7.7 mL/min.m2). Sex differences in GH clearance rates may account at least in part for the lower mean serum GH concentrations in pubertal, but not prepubertal, males compared to those in females. The differences in clearance between prepubertal children and adult women and men suggest that the male-female differences in GH clearance are due to androgen effects on GH clearance or on the relative proportions of free and protein-bound GH in serum.