Adrenalectomy is an operation to remove one of the adrenal glands. It is commonly performed to treat adrenal tumours or conditions that cause excess hormone production. The adrenal glands produce important hormones, including cortisol and aldosterone, which help regulate blood pressure, metabolism and the body's response to stress.

After adrenalectomy, some patients may develop adrenal insufficiency, a condition in which the body does not produce enough of these essential hormones. In severe cases, this can lead to an Addisonian (adrenal) crisis, a life-threatening emergency that can cause shock, organ failure and death if not treated promptly.

The risk of adrenal insufficiency after surgery depends largely on cortisol levels before the operation. In patients with Cushing's syndrome, where there is excessive cortisol production, the risk of adrenal insufficiency after adrenalectomy is almost 100%. For this reason, these patients routinely receive steroid replacement treatment after surgery to replace missing hormones and prevent adrenal crisis.

For other patients undergoing adrenalectomy, the best management approach is less clear. Patients with mild autonomous cortisol secretion (MACS) have a moderate risk of adrenal insufficiency - around 50-65%. Patients with normal cortisol secretion (NCS) may also develop adrenal insufficiency because one adrenal gland has been removed, occurring in around 20-37% of cases.

International medical guidelines currently disagree on how best to manage these patients after surgery. Some recommend measuring cortisol levels the morning after surgery and treating only if levels are low, while others recommend giving steroid treatment to all patients with mild cortisol excess. There is currently no clear guidance for patients with normal cortisol secretion.

This study will compare these management strategies to determine which approach best reduces the risk of adrenal insufficiency after adrenalectomy. The study will be conducted at King's College Hospital and will run for approximately two years.

Inclusion Criteria:

• Recommended for adrenalectomy following adrenal multidisciplinary discussion
• ≥18 years old
• Ability to consent

Exclusion Criteria:

• Overt Cushing's syndrome
• Pregnancy
• Pre-existing confirmed adrenal insufficiency
• Pre-existing steroid therapy (including high dose steroid inhalers)
• History of adrenalectomy
• Bilateral disease as assessed radiologically and clinically