Hormonal regulation of the peripubertal surge of insulin-like growth factor-I in the rat

Endocrinology. 1987 Feb;120(2):491-6. doi: 10.1210/endo-120-2-491.

Abstract

The marked increase in circulating insulin-like growth factor-I (IGF-I) levels during puberty observed in primates indicates an important functional relationship between hypothalamic-pituitary gonadal function and hormonal regulation of peripubertal circulating IGF-I levels. Recent studies demonstrating local production and secretion of gonadal peptides including IGF-I suggest that increased circulating IGF-I levels during puberty might be due to direct gonadal secretion of IGF-I or alternatively to indirect effects of increased gonadal steroid secretion on nongonadal tissues including the hypothalamus, pituitary, and liver. We therefore studied the effects of prepubertal castration on the pubertal IGF-I surge and demonstrate that castration provokes a further increase rather than ablation of the pubertal IGF-I surge in the rat. Furthermore, neonatal treatment with monosodium glutamate, a hypothalamic neurotoxin, abolishes the pubertal IGF-I surge when commenced on postnatal day 1 but not on day 5, whereas treatment with a GnRH antagonist commencing within 12 h of birth significantly reduces but does not abolish the pubertal IGF-I surge. We therefore propose that the pubertal IGF-I surge in the rat is not due to direct gonadal secretion of IGF-I or other gonadal hormones during puberty but may involve hypothalamic and/or hepatic programming by events during prenatal or very early postnatal life.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Female
  • Gonadotropin-Releasing Hormone / analogs & derivatives*
  • Gonadotropin-Releasing Hormone / pharmacology
  • Insulin-Like Growth Factor I / blood
  • Insulin-Like Growth Factor I / metabolism*
  • Luteinizing Hormone / blood
  • Male
  • Orchiectomy
  • Organ Size
  • Ovariectomy
  • Rats
  • Rats, Inbred WF
  • Sex Factors
  • Sexual Maturation*
  • Somatomedins / metabolism*
  • Testosterone / blood

Substances

  • Somatomedins
  • Gonadotropin-Releasing Hormone
  • Testosterone
  • surfagon
  • Insulin-Like Growth Factor I
  • Luteinizing Hormone