The final guideline of NICE on thyroid disease is now available. TUK will probably have the details. To my mind they are still stuck in the mud of redusing to budge unless randomized clinical trials are done to show combination benefit over mono therapy. I quote:
Combined levothyroxine and liothyronine vs levothyroxine alone
There was evidence of a clinically important benefit of combined levothyroxine and liothyronine in terms of two aspects of quality of life, although both outcomes came from short-term follow-up studies. A clinically important harm was associated with the combined use of levothyroxine with liothyronine compared to levothyroxine monotherapy in terms of one aspect of quality of life and TSH suppression. There was no clinically important difference between the two treatments in terms of general health-related quality of life and five different aspects of quality of life. Furthermore, no clinically important difference was seen in either depression or symptom scores. Overall, the committee agreed that the evidence was generally suggestive of combined therapy having no important effect on quality of life and the small and contradictory benefits and harms in subdomains of quality of life were more likely to reflect the low quality of the underlying evidence.
The committee were aware that the use of combination therapy is a critical issue in hypothyroidism. Based on the evidence available and the high costs of liothyronine (see section 1.7.2) the committee could not recommend the routine use of the combination therapy for the general population of people with hypothyroidism. The committee noted that in their experience some people do not appear to achieve sufficient response to levothyroxine and agreed that it is plausible that in this subgroup the addition of liothyronine may have greater benefit than in the general population alone. However, there were no studies exclusively in the population of people who had failed to respond sufficiently to levothyroxine. In the absence of supporting RCT evidence, the committee agreed it was not appropriate to recommend the routine use of liothyronine either alone or as combination therapy even in this subpopulation. However they made a high priority research recommendation for trials conducted in this subpopulation that could potentially support guidance in the future.