Substitution of liothyronine at a 1:5 ratio for a portion of levothyroxine: effect on fatigue, symptoms of depression, and working memory versus treatment with levothyroxine alone.
OBJECTIVE
To attempt to confirm a previous report of superior effectiveness of using two thyroid hormones rather than one hormone to treat hypothyroidism.


METHODS
This trial attempted to replicate prior findings, which suggested that substituting 12.5 microg of liothyronine (LT(3)) for 50 microg of levothyroxine (LT(4)) might improve mood, cognition, and physical symptoms in patients with primary hypothyroidism. Additionally, this trial aimed to extend the previous findings to fatigue and to assess for differential effects in subjects with low fatigue and high fatigue at baseline. A randomized, double-blind, two-period, crossover design was used. At an endocrinology and diabetes clinic, 30 adult subjects with primary hypothyroidism stabilized on LT(4) were recruited. Patients randomly assigned to treatment sequence 1 received their standard LT(4) dose in one capsule and placebo in another. Patients assigned to sequence 2 received their usual LT(4) dose minus 50 microg in one capsule and 10 microg of LT(3) in the other. At the end of the first 6 weeks, subjects were crossed over to receive the other treatment. Carryover and treatment effects were assessed by t tests.


RESULTS
Of the 30 enrolled study subjects, 27 completed the trial. The mean LT(4) dose was 121 +/- 26 microg/day at baseline. No significant differences in fatigue and symptoms of depression were found between treatments. Measures of working memory were unchanged. During substitution treatment, the free thyroxine index was reduced by 0.7 (P<0.001), total serum thyroxine was reduced by 3.0 microg/dL (P<0.001), and total serum triiodothyronine was increased by 20.5 ng/dL (P = 0.004).


CONCLUSIONS
With regard to the outcomes measured, substitution of LT(3) at a 1:5 ratio for a portion of baseline LT(4) yielded no better results than did treatment with the original dose of LT(4) alone.
Rodriguez
Tom
T
College of Nursing, Texas Woman's University, Institute of Health Sciences, Houston, Texas 77030, USA.
Lavis
Victor R
VR
Meininger
Janet C
JC
Kapadia
Asha S
AS
Stafford
Linda F
LF
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D018592:Cross-Over Studies; D003863:Depression / Q000188:drug therapy / Q000523:psychology; D004311:Double-Blind Method; D005221:Fatigue / Q000188:drug therapy / Q000523:psychology; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D007037:Hypothyroidism / Q000188:drug therapy* / Q000503:physiopathology / Q000523:psychology; D008297:Male; D008568:Memory / Q000187:drug effects; D008875:Middle Aged; D011674:Pulse; D011795:Surveys and Questionnaires; D013974:Thyroxine / Q000097:blood / Q000627:therapeutic use*; D014284:Triiodothyronine / Q000097:blood / Q000627:therapeutic use*
D014284:Triiodothyronine; D013974:Thyroxine