BACKGROUND: The impact of thyroid disease on patients undergoing coronary artery 
bypass grafting has been reported in only small series of selected patients.
METHODS: We investigated 30-day mortality of patients on thyroxine replacement 
therapy undergoing isolated coronary artery bypass grafting from 1993 to 2000 
and identified variables of importance for outcome.
RESULTS: A total of 3,631 patients (606 women) had isolated coronary artery 
bypass grafting of whom 58 patients (30 women) were treated for hypothyroidism. 
The mortality rate was higher among women with thyroxine replacement (16.7%, 95% 
confidence interval [CI] 5.6 to 34.7) than those without thyroxine replacement 
(5.9%, 95% CI 4.1 to 8.2; p = 0.02) and no difference between men with (3.6%, 
95% CI 0.1 to 17.8) and without (2.6%, 95% CI 2.0 to 3.2) thyroxine treatment (p 
= 0.8). Intake of diuretics (p < 0.001) was directly associated with mortality 
whereas intake of aspirin (p = 0.01), levothyroxine dose (p = 0.03), and serum 
thyroxine level (p = 0.01) were inversely associated with mortality among women 
on thyroxine replacement.
CONCLUSIONS: Women on thyroxine replacement therapy undergoing coronary artery 
bypass grafting had an increased mortality rate. We speculate that insufficient 
thyroid hormone replacement could partly play a role in this outcome.