L am 48, 1;m 145 lbs. I, m 5' 2" tall I have hipotiro. And drink Synthroid (thyroxine) 100mg how to lose weight?

Nutrition & exercise. Proper nutrition & regular exercise are key to losing & maintaining weight. Optimal thyroid function helps, too, so make sure your TSH is right for you (lots of debate over normal vs optimal). Check out http://nhlbisupport.Com/bmi/ to calculate your body mass index. Normal is <25 or less than 137# for 62". However, remember that body fat composition is more important than weight, especially if fat.