High TSH of 23 with RT3 Ratio of 14 Need Advice !!

I have a 95 year old mom whose lab results are as Followed :

TSH : 23.05 up from 12.56 (30 days prior.)

Free T4: 1.0 up from 0.8

Free T3: 2.4 up from 2.3

Reverse T3: 17 up from 13

Reverse T3 Ratio: 14.1 down from 17.69 ( Free T3 divided by RT3)

Currently on 75 mcg's of Levothyroxine (Synthroid) but doc wants to raise her to 100 mcg's !!!!

Any thoughts or suggestions would sincerely be appreciated.