It's just the fucking letter T, no meaning, nothing special, just the good old 21st letter of the alphabet
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Testosterone. Most commonly used by the Transgender community while discussing HRT (Hormone Replacement Therapy).
"I just started T!"
"I've been on T for a year now."
When someone blows their load on a baby girl then smothers her with her parents, while running from capture by the police because they robbed a Carls Jr