Letrozole is an effective aromatase inhibitor that can block the transformation of androgen to estrogen in vivo and is widely used in the construction of PCOS rat models, which can produce endocrine characteristics and ovarian morphological changes similar to clinical PCOS, including hyperandrogenemia, ovulation disorder, and obesity (24). Here, CYP19A1 is linked to obesity due to melanocortin 4 receptor deficiency.