In human studies, too, the vast majority of studies show higher ghrelin levels in hypothyroidism and lower ghrelin levels in hyperthyroidism (despite the often present increased appetite) [25, 26, 38, 42–44], with some showing a direct negative correlation between fT3 and ghrelin [26, 45] and some showing only group effects [38, 44]. This evidence concerns the gene GHRL and hyperthyroidism.