Glutamine

http://www.fluorideresearch.org/323/files/FJ1999_v32_n3_p162-170.doc
Flouride harms, but glutamine and glycine restore testosterone

Getting his act together: roles of glutamate, nitric oxide, and dopamine in the medial preoptic area.
https://www.ncbi.nlm.nih.gov/pubmed/16963001