Serum immunoreactive somatomedin levels in normal adults, pregnant women at term, children at various ages, and children with constitutionally delayed growth.

Immunoreactive somatomedin (IRSM) levels in term pregnancy material sera (MS) and newborn cord sera (CS) were higher and lower, respectively, than those in normal adults. IRSM levels in MS and CS were not correlated, suggesting that SM dose not cross the placenta. The similar levels of IRSM in arterial and venous CS suggest that the placenta does not produce SM. IRSM levels in CS were higher than those in newborn sera and were correlated with day 1 newborn sera, suggesting that the placenta may regulate fetal serum IRSM levels. Serum IRSM levels in normal children gradually increased from birth to peak levels at puberty. The mean levels of serum IRSM reached peak levels 2 yr earlier in females. Males near pubertal age with constitutionally delayed growth had lower serum IRSM levels than age-matched controls. Diagnostic measurements of serum IRSM in children requires comparison with age- and sex-matched controls. Serum SM levels may only approximately reflect the local concentrations or activities of SM in various tissues.