Circulating ghrelin in thyroid dysfunction is related to insulin resistance and not to hunger, food intake or anthropometric changes

Objective: Ghrelin is a gastric peptide that plays a role in appetite stimulation, energy balance and possibly in insulin resistance. Hyperthyroidism is a situation where negative energy balance and insulin resistance coexist, while in hypothyroidism a positive energy balance and normal insulin sensitivity predominate. We investigated ghrelin levels and their relationship with hunger, food intake and both anthropometric and insulin resistance parameters in patients with thyroid dysfunction. Design and methods: We studied 24 hyperthyroid and 17 hypothyroid patients before and after normalisation of thyroid hormone levels and their respective body mass. index (BMI)-matched control group. We measured plasma ghrelin levels, homeostasis model assessment of insulin resistance (HOMA-IR) index, a hunger score, mean three-day calorie intake and anthropometric parameters. Results: In hyperthyroidism, HOMA-IR index was higher (3.21 +/- 0.60 vs 1.67 +/- 0.15 mM mU/l; P=0.014, t test for independent data) and ghrelin levels were lower (463.6 +/- 36.4 vs 561.1 +/- 32.1 pg/ml; P = 0.041, Mann-Whitney U-test) than in its control group and both normalised after treatment (HOMA-IR: 2.289 +/- 0.38 mMmU/l; P = 0.106, t test for independent data, and ghrelin: 539.7 +/- 45.4 pg/ml; P=0.549, Mann-Whitney U-test). Glucose, as a component of HOMA-IR index was the only predictor for ghrelin levels (beta = -0.415, P = 0.044, stepwise multiple regression analysis). In hypothyroidism, HOMA-IR index and ghrelin levels were similar to those in its control group both before and after treatment. In both thyroid dysfunction states, no correlations were observed between changes in ghrelin levels and in free T4, free T3, anthropometric parameters, total calorie intake and hunger score. Conclusions: In thyroid dysfunction states, ghrelin levels seemed to be in relation to insulin resistance and not to energy balance and food intake regulation, as seen in other physiological and pathological states.