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インスリン様成長因子(IGF)は,かつてソマトメジンとも呼ばれていたが,IGF-Ⅰ(ソマトメジンC)とIGF-Ⅱの2種類存在する.IGF-Ⅰは,乳児期から年齢とともに上昇し,思春期を迎え成長率が最も高い時期にピークをとった後に低下していく.IGF-Ⅱは1歳以降の濃度はほぼ一定である.性腺ホルモンでは,テストステロン,エストラジオールともに新生児期に高い時期があった後は,男女ともに思春期発来までは測定感度以下である.思春期の発来とともに,上昇して成人の値に達する.女性では,性周期が完成すると卵胞初期と排卵期をそれぞれ最低値と最高値とする月内変動がみられるようになる.
Age-dependent changes of IGF (insulin-like growth factor)-Ⅰ, IGF-Ⅱ, testosterone, and estradiol from infancy through adolescence were outlined. During childhood, serum IGF-Ⅰ levels rise gradually, with attainment of adult levels at the onset of sexual maturation. They rise dramatically during puberty and gradually decline again to the adulthood levels. On the other hand, IGF-Ⅱ levels remain relatively constant throughout childhood. Testosterone and estradiol levels are high in the neonatal period, then decline to undetectable levels throughout childhood. They rise during puberty and attain the adulthood levels. Both chronological age and pubertal stage should be considered when these laboratory data are evaluated.
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