Adrenal gland tumour, gross specimen. This is an adenoma of the cortex (outer lining) of the adrenal gland. Although benign (non-cancerous), the growth can cause problems as it may lead to over- or under-production of the hormone cortisol (hydrocortisone), which the gland produces and secretes. Cortisol is responsible for regulating stress and energy levels. The immune and inflammatory response is also mediated to a large extent by its release. Over-production of cortisol leads to Cushing's Syndrome, which causes weight gain, muscle weakness, high blood pressure and psychological disturbances. In such cases, the gland is usually removed.