Effect of satiety on TSH and free thyroxin levels in healthy individuals and patients with subclinical and overt hypothyroidism

Abstract

Background: Thyroid stimulating hormone (TSH) and thyroxine levels may change according to fasting — satiety status. AIM: The aim of this study was to determine the effect of satiety on TSH and free thyroxine levels.Methods: This study was conducted in a tertiary hospital. According to previous TSH and thyroxine levels, groups of 30, 30 and 60 participants were designated as subclinical hypothyroidism, hypothyroidism, and control groups respectively. To obtain TSH and thyroxine results first phlebotomy was performed at 8 am while participants were in fasting state. Then participants were allowed to have non-standardized breakfast. Second phlebotomy was performed at 10 am while participants were in non-fasting state. Paired t-test and ANOVA were used to analyze the data.Results: The fasting TSH levels of the participants (2.57 ± 1.84 mlU/L) were significantly higher than the satiety TSH levels (2.04 ± 1.48 mlU/L) (t = 8.566, p < 0.001, d = 0.80). The fasting free thyroxine values (1.31 ± 0.38 mg/dl) of the participants were significantly lower than the satiety free thyroxine values (1.39 ± 0.35 mg/dl) (t = -1.988, p = 0.049, d = 0.20).Conclusion: Knowing how TSH and free thyroxine tests are affected by satiety has the power to affect treatment of many patients. Our study has shown that both TSH and free thyroxine levels changed significantly according to satiety status.