Plasma growth-promoting activity measured as thymidine activity in constitutionally short children.

Growth-stimulating activity of plasma was measured, both as thymidine activity using a lymphocyte bioassay and as sulfation activity using a cartilage bioassay, in 72 constitutionally short children aged 1-6 years and 38 age-matched controls. Plasma transferrin was also measured. No significant differences were found between the two groups. However, short children aged 1-3 years did not have higher thymidine activity than children aged 4-10 years, whereas in normals the thymidine activity was significantly higher in the first years of life. Thymidine activity was lower in female than in male constitutionally short children.