http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2774316/
Conclusion
Here we demonstrated that D-aspartic acid, which occurs as a physiological compound in the mammalian pituitary and testis, has a role in the regulation of the release and synthesis of LH and testosterone. In humans and rats, sodium D-Asp treatment enhances the release of LH and testosterone. The experiments that we carried out on rats have permitted us to understand that this amino acid regulates the synthesis of LH and testosterone in the pituitary and the testis respectively. This action is mediated in the pituitary by cGMP and in the testis by cAMP, which act as the second messengers in the signal transduction in the pituitary and testes respectively. The pituitary and testis possesses a D-Aspartate racemase, which provides the necessary production of D-Asp.