Thyroxine treatment in patients with symptoms of hypothyroidism but thyroid function tests within the reference range: randomised double blind placebo controlled crossover trial
Authors: M A. Pollock, A. Sturrock, K. Marshall, K. M Davidson, C. J G Kelly, A. D McMahon, E H. McLaren
Journal: BMJ (2001)

<h3>Abstract</h3> <b>Objectives:</b> To determine whether thyroxine treatment is effective in patients with symptoms of hypothyroidism but with thyroid function tests within the reference range, and to investigate the effect of thyroxine treatment on psychological and physical wellbeing in healthy participants. <b>Design:</b> Randomised double blind placebo controlled crossover trial. <b>Setting:</b> Outpatient clinic in a general hospital. <b>Participants:</b> 25 patients with symptoms of hypothyroidism who had thyroid function tests within the reference range, and 19 controls. <b>Methods:</b> Participants were given thyroxine 100 µg or placebo to take once a day for 12 weeks. Washout period was six weeks. They were then given the other to take once a day for 12 weeks. All participants were assessed physiologically and psychologically at baseline and on completion of each phase. <b>Main outcome measures:</b> Thyroid function tests, measures of cognitive function and of psychological and physical wellbeing. <b>Results:</b> 22 patients and 19 healthy controls completed the study. At baseline, patients9 scores on 9 out of 15 psychological measures were impaired when compared with controls. Patients showed a significantly greater response to placebo than controls in 3 out of 15 psychological measures. Healthy participants had significantly lower scores for vitality when taking thyroxine compared to placebo (mean (SD) 60 (17) <i>v</i> 73 (16), P&lt;0.01). However, patients9 scores from psychological tests when taking thyroxine were no different from those when taking placebo except for a poorer performance on one visual reproduction test when taking thyroxine. Serum concentrations of free thyroxine increased and those of thyroid stimulating hormone decreased in patients and controls while they were taking thyroxine, confirming compliance with treatment. Although serum concentrations of free triiodothyronine increased in patients and controls taking thyroxine, the difference between the response to placebo and to thyroxine was significant only in the controls. <b>Conclusions:</b> Thyroxine was no more effective than placebo in improving cognitive function and psychological wellbeing in patients with symptoms of hypothyroidism but thyroid function tests within the reference range. Thyroxine did not improve cognitive function and psychological wellbeing in healthy participants. <h3>What is already known on this topic</h3> Recent anecdotal accounts suggest that patients with symptoms of hypothyroidism but who are biochemically euthyroid may benefit from thyroxine treatment No controlled trials in this area have been reported <h3>What this study adds</h3> This study suggests that thyroxine is no more effective than placebo in improving psychological and physical wellbeing in patients who show symptoms of being clinically hypothyroid but whose thyroid function tests are within the reference range Thyroxine replacement did not improve psychological and physical wellbeing in healthy participants