INSR and hyperinsulinism: In Sprague-Dawley rats the serotonin-mediated activation of HPA axis exhibited a significant increase of body weight, of the abdominal circumference and the abdominal white adipose tissue mass, and in addition led to impaired glucose tolerance, fasting hyperglycemia, hyperinsulinemia, and significantly decreased expression of insulin receptor in the hypothalamus, indicating the development of central insulin resistance [88].