SUMMARY OF THE STUDY
The study was done in United Kingdom using a database called The Health Improvement Network. Adult patients who were diagnosed with hypothyroidism between January 1, 1995 and December 31, 2017 were included in the study. The main outcomes were heart disease involving the blood vessels, heart failure, and stroke. Secondary outcomes were risk of death, irregular heart rhythm, and broken bones.
There were 162,369 patients in the 22-year study period. A total of 863,072 TSH measurements were analyzed. Risk of heart disease related to damage to blood vessels was higher when TSH level increased over 10 mIU/L. The risk of stroke was slightly less when TSH level was between 3-3.5 mIU/L and 4-10 mIU/L. Risk of death was higher when TSH level was lower than 0.1 mIU/L or especially above 10 mIU/L. Broken bones were more common at TSH levels above 10mIU/L, especially in women older than 65 years old.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that there was no evidence of negative outcomes when TSH levels were maintained in the recommended reference ranges in the guidelines (0.4 – 4 mIU/L). Conversely, the risk of heart disease, stroke, broken bones and death was higher in hypothyroid patients with TSH levels outside the recommended reference range. Importantly, this range offers flexibility in treatment since patients may feel better at different TSH levels and the findings of this study support that this is a safe range.
— Ebru Sulanc, MD