**5.2. Resistin**

Since obesity is considered a global epidemic and one of majors public health problem, affecting developed and developing countries [185, 186], and obese subjects may presente increased resistin levels [46], which can worse insulin resistance and inflammation [119], one of the most used strategies is the weight loss by reduction of caloric intake [187]. Caloric restriction affects the regulation of adipose tissue gene expression, normalizing the adipokines changes caused by obesity [10], while thyroid hormones play a central role in regulating adipose tissue metabolism [83], being related to body weight changes, thyroid hormones may therefore play a key role in the normalization of resistin in weight loss.

Nogueiras et al. [130] show a decrease in resistin mRNA expression in epididymal adipose tissue of pregnant and nonpregnant rats that were subjected to food restriction. Kim et al. [188] showed that resistin mRNA levels were decreased during fasting, but increased considerably when the animals were refed or after insulin infusion. T3 had no effect on resistin mRNA levels in adipose tissue of obese animals submitted to calorie restriction [189].

Normalization of circulating thyroid hormones was accompanied by a significant decrease in resistin concentrations [126]. Others showed that hyperthyroid patients exhibit a significant decrease in resistin levels compared with euthyroid individuals, and the normalization of circulating thyroid hormones was not accompanied by any significant change in resistin levels [127]. After adjusting the weight by the body mass index, the resistin levels in hyperthyroid patients were similar to euthyroid subjects [128] (Figure 4).

The association between thyroid hormone and resistin in weight loss present conflicting data, requiring further studies to evaluate this relation.
