Obesity is a symptom caused by dysfunction of the hypothalamus, so diet alone cannot be therapeutic. In recent years, it has been observed that weight loss is accelerated by human chorionic gonadotropin (hCG) hormone preparation used for hypothalamic dysfunction in obesity treatment in both sexes. Beta hCG is also used for in vitro fertilization and in treatment of hypogonadotropic hypogonadism. Our aim was to investigate the immunohistochemical and the ultrastructural changes of the rat hypophysis, adrenal gland, testis and ovary tissue to demonstrate effects of a single dose daily subcutaneous injection of the beta hCG. In this study, 10 obese female, 10 obese male, 10 non-obese female and 10 non-obese male rats were used. In each group, single dose of subcutaneous beta hCG injection has been applied to 7 rats for 5 weeks in 5 days of the week, and placebo has been applied to the remaining 3 rats. At the end of 5 weeks, after perfusion fixation, tissues were removed and sections were collected for immunohistochemical and ultrastructural studies. There weren’t any clear differences in tissues and it was thought that the increases and decreases in the number of hormone receptors might be seen in parallel with the increases and decreases in hormone levels. In conclusion, the implementation of beta hCG in addition to diet, has no effect on hypophysis, adrenal glands, testicles and ovaries