Osteoporosis is a chronic skeletal disease which leads to a decrease in bone strength which increases the risk of fractures. Clinically overt hypercortisolism leads to hypertension, central obesity, diabetes and osteoporosis. More recently, even the condition of mild and asymptomatic hypercortisolism has been associated with increased prevalence of chronic complications of cortisol excess and mortality. In patients with osteoporosis this form of hypercortisolism may remain occult (hidden hypercortisolism, HidHyCo). Although asymptomatic, however, this subtle cortisol excess is associated with an increased risk of osteoporosis and fragility fractures. Moreover, HidHyCo prevalence seems to be increased in osteoporotic patients. The HidHyCo case finding is of utmost importance. However, given the high prevalence of bone fragility and the relatively low diagnostic accuracy of the currently available tests for the HidHyCo detection, a mass screening for HidHyCo is considered unthinkable. As now, no guidelines are available for addressing the HidHyCo screening in osteoporosis. Therefore, the aims of the present study are the following: i) to assess the HidHyCo prevalence in a sample of osteoporotic patients; ii) to compare the clinical characteristics between osteoporotic/osteopenic patients with HidHyCo and those without HidHyCo in order to determine the clinical characteristics more frequently associated with the HidHyCo presence and to identify those osteoporotic patients worthy of HidHyCo screening; iii) to further investigate bone quality and turnover in HidHyCo patients, to characterize HidHyco patients from a molecular and genetic point of view and to evaluate the pathogenetic mechanisms explaining the negative effects of endogenous cortisol excess on bone health in these patients and the potential role of the genetic background and of the gut microbiome. The HidHyCo could be present in a not negligible percentage of osteopenic/osteoporotic patients. In these patients, osteoporosis and, if present, other comorbidities can improve by the surgical resection of the adrenal or pituitary adenoma if feasible, or by the use of drugs able to modulate cortisol secretion or glucocorticoid sensitivity. Moreover, the case-finding could be reserved in those patients at higher risk of having HidHyCo, therefore, reducing the costs of a scarcely specific mass screening.