Hi everbody..I'm new here and this is my first time posting, I don't understand what T3 and T4 means could someone please explain it to me? I keep hearing T3 is best medication wise but don't even know what it is. All I know is I have hypothyroidism and take 100mg Levothyroxine for it. I have had it about 17 years. Is there something better medication wise out there that I'm missing out on? Thanks.