Changes of serum allopregnanolone levels in the first 2 years of life and during pubertal development

Allopregnanolone is the best characterized among neurosteroids, and its rol e in the control of neuroendocrine axes has attracted increasing interest r ecently. However, there is no available information about circulating level s of allopregnanolone during infancy, childhood and puberty. We studied two groups of children: I) those aged between 0 and 2 y (n = 72). and 2) those aged between 6 and 18 y, at different Tanner's stages (n = 82). In each of these patients, serum allopregnanolone, progesterone, cortisol, and dehydr oepiandrosterone levels were evaluated after informed consent; allopregnano lone was measured by RIA after acid extraction on cartridge. There was no s ignificant variation of serum allopregnanolone levels either in male and fe male children during the first 2 y of life. Furthermore, although serum deh ydroepiandrosterone levels showed a significant decrease, inversely correla ted with age of the children (p < 0.01), serum cortisol and progesterone le vels showed a significant age-related increase during the first 2 y of life . Cortisol and allopregnanolone levels were: positively correlated (p < 0.0 1). During puberty, we observed a progressive increase in serum allopregnan olone levels in both boys and in girls, which were higher at Tanner' s stag e IV-V (0.7 +/- 0.01 nM; mean +/- SEM) than at stages I-II(0.32 +/- 0.02 nM ; p < 0.01); mean levels were significantly higher at puberty than in the f irst 2 y of life (p < 0.01). Furthermore, during puberty, serum progesteron e and dehydroepiandrosterone levels also increased progressively with age i n both boys and girls. Allopregnanolone and dehydroepiandrosterone levels w ere positively correlated throughout puberty. The present results indicate that serum allopregnanolone levels do not change during the first 2 y of li fe but increase during pubertal development, suggesting that this steroid m ay be involved in the adaptive neuroendocrine mechanisms related to puberty .