Influence of thyroid function on the outcome of percutaneous coronary intervention in euthyroid patients with coronary artery disease

Background
Thyroid hormonal disturbance plays an essential role in coronary artery disease (CAD) development and progress. Few studies have detected the relation between percutaneous coronary intervention (PCI), thyroid gland function, and morphology. We aimed to assess the influence of baseline thyroid function tests on the outcome of PCI in euthyroid patients with CAD, and to detect the effect of PCI on the thyroid function and ultrasound features.
Patients and methods
This study included 113 clinically euthyroid patients with stable CAD. Serum free T3, serum free T4, thyroid-stimulating hormone (TSH), thyroid-stimulating hormone index, free T3/T4 ratio, anti-thyroperoxidase (TPO), and high-sensitivity C-reactive protein had been measured before, and then 24 h and 3 months after PCI. The morphology of thyroid was evaluated through thyroid ultrasound before and 3 months after PCI.
Results
One day after PCI, there was a significant increase in serum FT3 and serum FT4 and no significant change in the serum TSH compared with just before PCI ( < 0.001, = 0.04, = 0.97, respectively). In addition, there was a significant increase in serum FT3/FT4 ratio compared with just before PCI ( = 0.007). Three months after PCI, there was a significant increase in serum FT4, decrease in serum FT3 returning to baseline, and a significant increase in serum TSH compared with just before PCI ( = 0.42, < 0.001, < 0.001, respectively). There was a significant decrease in the serum FT3/FT4 ratio and significant increase in serum thyroid-stimulating hormone index compared with just before PCI ( ≤ 0.001, < 0.001, respectively). Higher TSH and measured echogenicity index were independent pre-PCI predictors of unfavorable outcomes after 24 h with cutoff values greater than 0.95 mIU/ml and greater than 1.81, respectively. Lower FT3 and higher FT4 levels were independent pre-PCI predictors of unfavorable outcomes after 3 months with cutoff values less than or equal to 2.95 pg/ml and greater than 1.3 ng/dl, respectively.
Conclusion
A state of euthyroid hyperthyroxinemia was detected 24 h after PCI. A state of thyroid hormone resistance was detected 3 months after PCI. Higher TSH and measured echogenicity index independently predicted unfavorable outcome after 24 h. Lower FT3 and higher FT4 levels independently predicted unfavorable outcomes after 3 months.