Serum bone Gla-protein as a marker of bone growth in children and adolescents: correlation with age, height, serum insulin-like growth factor I, and serum testosterone. - Johansen,J.S.; Giwercman,A.; Hartwell,D.; Nielsen,C.T.; Price,P.A.; Christiansen,C.; Skakkebaek,N.E. (J Clin Endocrinol Metab, 1988)