For example, serum IGF-1 levels have been shown to be negatively correlated with age [23–26] and BMI [27] in healthy adults and are modulated by medical conditions, which occur frequently in the elderly, for example, diabetes mellitus [28,29], depression/anti-depressant medication [30,31] or thyroid dysfunction [32]. The gene discussed is IGF1; the disease is depressive symptom measurement.