Adrenal incidentalomas and insulin resistance - a simple coincidence or a complex syndrome?
As non-invasive imaging techniques, such as sonography, become more and more available, there is a growing incidence of diagnosing of non-fuctioning adrenal tumors. They are usually called adrenal incidentalomas due to absence of any evident clinical manifestations. Adrenal incidentalomas are found in 2-8% population. Although generally non-funtioning, those tumors may secrete abundant quantities of steroid hormones and thus evoke glucose intolerance, lipid disorders, thromboembolic events and hypertension. Besides, insulin and insulin-growth factor exert mitogenic action on adrenocortical cells.
Here, the analysis of insulin resistance among 17 patients with adrenal incidentalomas is presented. Insulin resistance was assessed during oral 75 g glucose test (glycaemia and insulin concentration were measured). Hormonal analysis comprised ACTH level, cortisol before and after dexamethasone, DHEA, aldosterone and chromogranin A concentration. All patients were insulin-resistant. Five had diabetes mellitus and the rest of the patients presented with glucose intolerance. Two of the patients underwent adrenalectomy as the tumors were larger than 4 cm. The histological examination revealed adrenal adenomas. Six months following surgery one of the patients has normal insulin concentration, whereas the other still suffers from hyperinsulinaemia.
Therefore, it remains unclear whether the insulin resistance if the cause, or the consequence of the adrenal incidentaloma.