Thyroid Hormone Curbs Appetite and Blood Sugar by Lowering Ghrelin in Obese Rats

The global prevalence of obesity and Type 2 Diabetes continues to rise, necessitating novel therapeutic strategies. Thyroid hormones (THs) are critical regulators of metabolism, influencing energy expenditure, glucose homeostasis, and lipid metabolism. Ghrelin, often termed the 'hunger hormone,' is a potent orexigenic peptide that stimulates appetite and promotes fat storage. While the individual roles of THs and ghrelin in metabolic regulation are well-established, the precise interplay between thyroid hormone signaling and ghrelin secretion in the context of metabolic dysfunction, particularly in an obesity model, remains less understood. This study specifically aimed to elucidate whether thyroid hormone modulates food intake and glycemia through its effects on ghrelin secretion in a relevant animal model of metabolic disease.

The administration of thyroid hormone significantly impacted metabolic parameters in Zucker fatty rats. Treated animals exhibited a substantial reduction in daily food intake, averaging 23% less than the control group (p<0.01). This reduction in caloric intake translated to a significant decrease in body weight, with the treatment group showing a 15% lower final body weight compared to controls (p<0.001). Furthermore, glycemic control was markedly improved; fasting blood glucose levels were reduced by 32% (p<0.001), and plasma insulin levels decreased by 28% (p<0.05), indicating enhanced insulin sensitivity. The study's most critical finding revealed a direct mechanistic link: > Thyroid hormone treatment led to a robust suppression of plasma ghrelin concentrations by 41% (p<0.001) and a 2.5-fold decrease in hypothalamic ghrelin mRNA expression (p<0.01), strongly suggesting that the observed improvements in food intake and glycemia were mediated, at least in part, by reduced ghrelin signaling.