Here is a new study - just published in 2018:
"Effects of Long-Term Combination LT4 and LT3 Therapy for Improving Hypothyroidism and Overall Quality of Life"
Anam Tariq, Yijin Wert, Pramil Cheriyath, and Renu Joshi.
South Med J. 2018 Jun; 111(6): 363–369.
Published online 2018 Jun 1. doi: 10.14423/SMJ.0000000000000823
Yet again this points the way to more enlightened treatment.