He was born with tiny testicles, but they never descended. Also they were never surgically fixed down in the scrotum (orchiopexy). When he was 10 his testicles were found to have "disappeared" (testicular atrophy) because of the temperature up there. His testosterone level stayed as low as with girls. Still, he clearly identified as a man and was put on testosterone hormone therapy (a gel). When he takes a lot of testosterone for a few days he becomes really horny and hard and cums as a full man, but his cum is a clear, runny, sticky, smelly liquid. It is mostly prostatic fluid, just like with castrated shemales / trannies, but they hardly ever cum (much) as thery do not use testosterone replacements.