MSG treatment reduced the weight and volume of the testes and differentially influenced testosterone secretion in vivo. The pups were injected until d14 (prepuberty), d28 (puberty), or d56 (adult) with MSG or NS. Then the mice were sacrificed under anesthesia at 10 o’clock. The testicular weight and volume were measured for all MSG-treated and NS-treated mice (A, B) at all ages that were tested. ELISA analysis showed that the testosterone level of the 14MSG mouse plasma was slightly higher than that of the NS group; however, the difference was not significant (p > 0.05). Testosterone concentrations of the 28MSG mice increased compared with the 28NS-treated mice; however, the testosterone secretion in the 56MSG mice had a marked reduction (p < 0.05) (C). NSD, non-significant difference.