PTH and heart failure: This increase in IL-10–an antiinflammatory cytokine- levels after the treatment confirms the antiinflammatory activity of vitamin D. In a study by Schleithoff et al., adult patients being followed for heart failure and taking vitamin D were found to experience a significant increase in IL-10 levels, a decrease in PTH and TNF-α levels, and an increase in 25-hydroxyvitamin levels at the end of 6 weeks [14].