High ratios of free to total insulin-like growth factor-I in early infancy

Yukihiro Hasegawa, Tomonobu Hasegawa, Katsura Fujii, Hideko Konii, Makoto Anzo, Taiji Aso, Shinobu Koto, Makoto Takada, Yutaka Tsuchiya

研究成果: Article査読

36 被引用数 (Scopus)


Insulin like growth factor-I (IGF-I) is a major effector of somatic growth and metabolism. In normal, nonpregnant plasma, most of the IGF-I is complexed to specific IGF-binding proteins (IGFBPs), particularly IGFBP-3; only a minor fraction of plasma IGF-I exists in a free form. Recently, we have reported that free IGF-I levels, as measured using a new immunoradiometric assay, are relatively high in maternal plasma during pregnancy because of increased IGFBP-3 proteolytic activity. These high free IGF-I levels are physiologically important for the growth of maternal tissues such as uterus and placenta, which are related to the fetal growth. Growth during early infancy may be a continuation of fetal growth. In the present study, we have analyzed free and total plasma IGF-I and IGFBP-3 proteolytic activity in early infancy. Although the levels of free and total IGF-I were not significantly different in early infancy as compared with prepubertal periods, the ratio of free to total IGF-I (mean = 2.04%) was relatively increased and was similar to the ratio in pregnancy plasma (1.86%). However, unlike in maternal plasma, the high ratios were not totally caused by increased IGFBP-3 proteolytic activity. Our results suggest that there may be an increased conversion of plasma IGF-I to a free form in early infancy. The resultant increase in IGF-I bioavailability could contribute to the rapid somatic growth in early infancy.

ジャーナルJournal of Clinical Endocrinology and Metabolism
出版ステータスPublished - 1997 1月 1

ASJC Scopus subject areas

  • 内分泌学、糖尿病および代謝内科学
  • 生化学
  • 内分泌学
  • 臨床生化学
  • 生化学、医学


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