Endocrine Abstracts

Introduction: A recent meta-analysis has suggested that combined replacement with Liothyronine (T3) and Levothyroxine (T4) confers no additional benefit to patients with hypothyroidism but patients still occasionally request this treatment approach.

Aim: To analyse the indications and biochemical characteristics of patients on T4/T3 combination therapy for Hypothyroidism in our cohort of patients.

Methodology: A retrospective search of hypothyroid patients on T3 presenting between January 1997 and October 2006 using Clinical Workstation and Chemical pathology database was performed.

Results: A total of 4518 patients were treated with T4 of which 39 patients (0.8%) received T3 at some stage of treatment. The indications for T3 were: (a) Persistent symptoms despite biochemical euthyroidism (n=15);(b) Patient preference (n=6);(c) Thyroxine intolerance (n=3);(d) Thyroid cancer (n=2);(e) Thyroxine rash (n=1); (e) Thyroxine resistance (n=1).The indication for T3 was not documented in 11 patients.

32 patients were treated with T4 and T3 simultaneously and 14 patients (44%) continued T4/T3 combination (Median doses of T3 and T4are 20 mcg/day (10–30 mcg/day) and 125 mcg/day respectively (100–200 mcg/day).Three patients are on T3 alone due to T4 resistance or intolerance.

The mean fT3 was 6.72 pmol/L (3.5–6.5), fT4 16.25 pmol/L (9–25) and TSH 1.1 miu/L (0.3–5 miu/L). Importantly 7 patients (50%) on T3/T4 had TSH levels <0.05 for over 12 months.

Conclusion: There appears to be a small cohort of patients with hypothyroidism who elect to remain on T3.The placebo effect cannot be excluded in the group who report improved symptoms. The suppressed TSH in 18% is of concern due to risks of atrial fibrillation and osteopenia. We suggest that T3/T4 combination should be the exception rather than the rule and such patients should be followed up in a specialist clinic.