Crawford B A, Handelsman D J
Department of Obstetrics and Gynecology, University of Sydney, Australia.
J Clin Endocrinol Metab. 1996 Jan;81(1):65-72. doi: 10.1210/jcem.81.1.8550796.
To examine the role of androgens in initiating the pubertal rise in circulating insulin-like factor-I (IGF-I) levels, a longitudinal study of puberty in 13 male hamadryas baboons was conducted over 3 yr. The five control baboons commenced puberty (initial testicular enlargement) at a mean +/- SE age of 4.2 +/- 0.4 yr. Another eight baboons were castrated prepubertally; of those four received testosterone pellets (dose equivalent: 12.5-50 mg every 6 weeks) implanted se from the time of puberty. Body weight, crown-rump length, and limb length measurements, synchronized to pubertal onset, suggest that a pubertal growth spurt occurs in male baboons. Control baboons had a marked rise (4- to 5-fold; P < 0.0001) in circulating IGF-I levels; maximum IGF-I levels (168 +/- 9 nmol/L) were reached 42 months after the onset of puberty (mean chronological age 7.5 yr). Castrated baboons had no significant rise in IGF-I levels, however, administration of testosterone resulted in a close approximation of the normal pubertal rise in IGF-I (maximum values 140 +/- 8 nmol/L), confirmed by comparison of fitted sigmoid curves (r2 > 0.99; chronological age ED50 controls, 4.4 +/- 0.1 yr and castrate + testosterone, 4.3 +/- 0.1 yr). Serum IGF binding protein-3 levels paralleled the rise in IGF-I consistent with a common regulatory mechanism. In another study, castration of four sexually mature male baboons aged 11.12 +/- 1.16 yr had no effect on serum IGF-I levels (P = 0.5). This indicates that androgens are the predominant determinant of circulating IGF-I in the male baboon, and that this is an uniquely pubertal phenomenon.
为研究雄激素在启动青春期循环胰岛素样因子-I（IGF-I）水平升高过程中的作用，对13只雄性阿拉伯狒狒进行了为期3年的青春期纵向研究。5只对照狒狒在平均±标准误为4.2±0.4岁时开始进入青春期（最初睾丸增大）。另外8只狒狒在青春期前被阉割；其中4只从青春期开始时起接受皮下植入睾酮丸剂（剂量当量：每6周12.5 - 50毫克）。与青春期开始同步进行的体重、顶臀长度和肢体长度测量表明，雄性狒狒会出现青春期生长突增。对照狒狒循环IGF-I水平有显著升高（4至5倍；P < 0.0001）；青春期开始后42个月达到最大IGF-I水平（168±9纳摩尔/升）（平均实际年龄7.5岁）。阉割后的狒狒IGF-I水平无显著升高，然而，给予睾酮后，IGF-I水平接近正常青春期升高水平（最大值140±8纳摩尔/升），通过拟合S形曲线比较得到证实（r2 > 0.99；实际年龄ED50对照组为4.4±0.1岁，阉割+睾酮组为4.3±0.1岁）。血清IGF结合蛋白-3水平与IGF-I的升高平行，这与共同的调节机制一致。在另一项研究中，对4只年龄为11.12±1.16岁的性成熟雄性狒狒进行阉割，对血清IGF-I水平无影响（P = 0.5）。这表明雄激素是雄性狒狒循环IGF-I的主要决定因素，且这是一种独特的青春期现象。
