I have notice when i'm doing bench press for examble (pushing a big load for my abilities) a stimulation in testicles like the
HCG stimulation does in testes.I do not know if it is LH or other hormone does that, but is something triggers for more strength in this moment so as to be able to manage the effort.That;s why it is said that a big stress can deacrease or increase?testosterone.
IMO is much a neurotransmitter issue than a single hormone,maybe a neurochemical signal for T production either directly in testes either in LH,GNRH,DHEA.
Human brain is the greatest mystery.