THRB and obesity due to melanocortin 4 receptor deficiency: The OPRM1 gene, linked to the mu-opioid receptor, affects obesity and pain, especially in NOWS infants, with prolonged opioid use disrupting appetite and metabolism, leading to weight gain (111); NPY regulates appetite and energy balance, promoting feeding behavior and fat storage, thereby contributing to obesity development; THRB regulates metabolism and energy expenditure through thyroid hormones, affecting metabolic rate and potentially causing obesity if dysregulated.