Triiodothyronine (T3) is one of two major hormones produced by the thyroid gland, a small butterfly-shaped organ that lies flat across the windpipe at the base of the throat. The other major thyroid hormone is called thyroxine (T4), and together they help control the rate at which the body uses energy. Almost all of the T3 (and T4) found in the blood are bound to protein. The rest is free (unbound), and is the biologically active form of the hormone.
Sheba researchers conducted a retrospective study of 54 adults hospitalized at Sheba Medical Center with COVID-19 and normal thyroid gland function. The study population was divided into 3 groups based on their free T3 levels, and the results showed that the mortality rates among the low free T3 levels group were 40% higher compared to the control groups, while the prevalence of patients who required mechanical ventilation was 45% higher.
“We expected to find an association. What surprised us was the robustness of the association and the high significance it retained when adjusted for other variables,” said Dr. Yair Schwarz of the Dalia and David Arabov Endocrinology and Diabetes Research Center at Sheba Medical Center. According to Schwarz: “Future research should focus on the time-old question of whether treatment of low T3 levels provides any benefit concerning morbidity and mortality. Today there is a lack of current high quality research in the area.” He added that for the time being: “The implications of the findings will provide another potential evaluation tool for a physician treating COVID-19 patients.”
