The present invention provides non-invasive methods for determining the beta cell mass in the pancreas of a subject by administering to the subject an effective amount of a vesicular monoamine transporter type 2 (VMAT2)-specific radioligand obtaining at least one computerized image of at least a portion of the pancreas of the subject and quantitatively analyzing the computerized image in order to determine the beta cell mass in the pancreas of the subject. The present invention additionally provides methods for diagnosing a metabolic neuroendocrine disorder in a subject including insulinoma, diabetes and preclinical diabetes, as well as methods for determining the efficacy of treatment for a metabolic disorder. The present invention further provides methods for assessing the prognosis of a subject at risk for developing diabetes, and methods for managing the treatment or prevention of diabetes. The present invention also provides kits for use in determining the beta cell mass in the pancreas of a subject, as well as diagnosing metabolic or neuroendocrine disorders in a subject.
