"Human chorionic gonadotropin (HCG) administration in L-tryptophan treated rats for 21 days increased the plasma testosterone level in spite of increased brain 5-HT level."
Just grab you some hcg
Judging solely from the abstract, it appears to be saying that higher levels of 5-HT in the brain correlates with lower testosterone levels. But is it only when those levels are elevated due to trytophan dosing? Or are high 5-HT levels always indicative of lower T? Probably not that cut and dried. Reminds me of the vitamin D study where subjects with higher D levels had higher T.