Objective: Agouti related peptide (AgRP), the endogenous antagonist of the melanocortin 3 and 4 receptors, is expressed at high levels in the arcuate nucleus of the hypothalamus. Some studies have demonstrated that intracerebroventricular AgRP administration increases plasma LH, FSH, testosterone levels. It also increases hypothalamic LHRH release in vitro, an effect that can be prevented by addition of melanocyte stimulating hormone. These findings suggest that AgRP may play a role in the control of the hypothalamo-pituitary gonadal axis. Our aim in this study was to investigate plasma AgRP levels in male hypogonadal patients.
Research design and methods: Thirty males with hypogonadotropic hypogonadism were included in this study. Twenty healthy male subjects were served as controls. A thorough physical exam was performed in all participants. After an overnight fasting, blood samples were drawn, centrifuged and studied collectively. Serum total and free testosterone, FSH, LH, cortisol, free thyroxine, thyroid stimulating hormone, prolactin, and sex hormone binding globuline were measured using by radioimmunoassay method. Plasma AgRP levels were measured with a commercial ELISA kit.
Results: Serum testosterone and gonadotropin levels differed significantly between patients and controls (P<0.001). Plasma AgRP levels of the patients (3.28±0.32 ng/ml) were found to be lower than those of controls (4.64±0.28 ng/ml) (P<0.01).
Conclusion: This is the first study that investigates plasma AgRP levels of male patients with hypogonadotropic hypogonadism. Our limitations were small sample size and no dynamic investigation. However, this study showed that there might be a relation between AgRP and androgenic hormone deficiency. It should be done more comprehensive and prospective studies to draw a clearer conclusion on this subject.