In situations where GHRH expression increases (GH deficiency due to GH gene mutations, hypothyroidism, etc.), pituitary ghrelin expression also increases; conversely, when hypothalamic GHRH expression decreases (GH replacement therapies, glucocorticoid treatments, hyperthyroidism, etc.), pituitary ghrelin expression also decreases. This evidence concerns the gene GH1 and hyperthyroidism.