However, a negative association between serum ghrelin level and bone mass or bone synthesis marker PINP has been observed in either female suffered from anorexia nervosa or obesity patients who have weight loss, and this is probably attributed to the elevated adrenocorticotropic hormone (ACTH) level induced by ghrelin (Arvat et al., 2001; Misra et al., 2005; Yu et al., 2022). Here, GHRL is linked to obesity due to melanocortin 4 receptor deficiency.