Platelet monoamine oxidase in healthy 9-and 15-years old children: The effect of gender, smoking and puberty

I The effect of gender, smoking and pubertal development on platelet monoam ine oxidase (MAO) activity was described in a randomly selected, large samp le of 9- and 15-years old healthy children. 2. Platelet MAO activity was measured in 1129 children by a radioenzymatic method with beta -phenylethylamine as the substrate. Smoking habits were re ported in an anonymous questionnaire. Pubertal status was assessed visually using Tanner's stages. 3. Boys, younger children and smokers had significantly lower platelet MAO activity than girls, older children and non-smokers, respectively. Girls in Tanner's stage V for breast and pubic hair development had significantly l ower MAO than girls in stage IV. 4. Differences in gender, age, pubertal status and smoking habits must be t aken into account if the relationship between platelet MAO activity, person ality and psychiatric disorders is studied in children.