A randomized double-blind crossover trial to investigate the efficacy of screening for adult hypothyroidism

Objective To assess the value of population screening for adult hypothyroidism. Setting Healthy people attending for a general health assessment. Methods A thyroid-stimulating hormone (TSH) measurement was performed on people attending for a general health assessment (women aged 50-79 [35-49 with a family history of thyroid disease] and men aged 65-79). Those with TSH levels above 4.0 mU/L were invited to join a randomized double-blind crossover trial of thyroxine and placebo, each given in random order for four months. On entry a second blood sample was collected for a TSH measurement after the end of the trial to determine whether this would help select individuals for thyroxine treatment. The daily thyroxine dose started at 50 mu g and if necessary was increased to achieve a TSH level of 0.6-2.0 mU/L. Results There were 341 (8%) people with a TSH level above 4.0 mU/L, 110 met eligibility criteria (64 agreed to participate), and 56 (49 women, 7 men) completed the trial. Among the 15 individuals with a repeat TSH measurement above 4.5 mU/L, 11 reported feeling better on thyroxine than placebo and none reported feeling better on placebo (P = 0.001; four felt no different), indicating that in this group 73% benefitted (i.e. 11/15; 95% Cl 45-92%). The main symptoms relieved were tiredness and loss of memory. There was no indication of harm. In the 41 individuals with a repeat serum TSH of 4.5 mU/L or less: 10 reported feeling better on thyroxine than placebo and 16 better on placebo (P = 0.42, 15 felt no different). Thus about 8% of men and women in the specified age groups had a TSH above 4.0 mU/L, and of these about a quarter had a repeat TSH above 4.5 mU/L, of whom about half would benefit from thyroxine treatment. Conclusion The results indicate that screening for hypothyroidism would be worthwhile. Approximately 1% of people screened would have a better quality of life. Pilot screening programmes for adult hypothyroidism are justified.