As a natural endogenous inhibitor of Pcsk1 (prohormone converting enzyme 1), Pcsk1n slows down the mediating effect of hormone converting enzyme and promotes food intake and obesity [29, 33], and Pcsk1 gene mutations are common in the obese human population [30–32]. The gene discussed is PCSK1N; the disease is obesity due to melanocortin 4 receptor deficiency.