Other researchers have interpreted the frequent observation of isolated TSH elevation in obesity as a mere manifestation rather than functional defect, resulting from deranged hypothalamic-pituitary axis or effects of increased leptin on TRH production and type 2 iodothyronine deiodinase (D2) inhibition in the thyrotrophs [26]. Here, TRH is linked to obesity due to melanocortin 4 receptor deficiency.