ACTH Adenoma (Cushing's Disease)
An ACTH-secreting pituitary tumor stimulates the adrenal glands to overproduce cortisol, causing Cushing's disease. Cushing's disease is the most common cause of endogenous Cushing's syndrome. Although it is a benign pituitary neuroendocrine tumor (PitNET), uncontrolled cortisol excess produces serious systemic consequences.
마지막 업데이트: 2026-06-07
Definition and Terminology
ACTH adenoma (corticotropinoma) is a benign tumor arising from the corticotroph cells of the anterior pituitary that secretes adrenocorticotropic hormone (ACTH). In the 2022 WHO classification it is defined as a TPIT-lineage pituitary neuroendocrine tumor (PitNET). An important distinction applies here: 'Cushing's disease' refers specifically to cortisol excess due to a pituitary ACTH adenoma, whereas 'Cushing's syndrome' is the general term covering all causes of cortisol excess (pituitary, adrenal, ectopic ACTH or external steroid use).
Epidemiology
Cushing's disease is the most common cause of endogenous Cushing's syndrome (that is, not due to external steroid use). It is markedly more frequent in women than men and is seen most often in women of reproductive age. The great majority of tumors are small (microadenomas, under 10 mm), which can make them difficult to image.
Symptoms
Symptoms arise from the effects of chronic cortisol excess on tissues and usually develop over years. Typical findings include central (trunk-predominant) weight gain, a rounded face ('moon face'), fat accumulation over the neck and upper back, easy bruising and wide purple stretch marks (striae), and thinning of the arms and legs with muscle weakness. Commonly associated conditions are hypertension, diabetes or impaired glucose tolerance, bone loss (osteoporosis) and neuropsychiatric symptoms such as depression and anxiety. A tendency to infection due to immune suppression may also be seen.
Diagnosis
Diagnosis is a two-step process. The first step confirms cortisol excess, using tests such as 24-hour urinary free cortisol, late-night salivary cortisol and the low-dose dexamethasone suppression test; consistent positivity of at least two tests is generally sought. The second step identifies the source of the excess: the plasma ACTH level helps distinguish ACTH-dependent causes (pituitary or ectopic) from ACTH-independent causes (adrenal). Pituitary MRI is valuable for showing the adenoma, but a significant proportion of small adenomas may not be visible; in that case the gold standard for distinguishing a pituitary from an ectopic source is an invasive test called bilateral inferior petrosal sinus sampling (BIPSS).
Treatment Options
First-line treatment is endoscopic transsphenoidal surgery; in experienced hands, remission rates are high, especially for small adenomas visible on MRI. A very low morning cortisol level after surgery indicates successful removal, and cortisol replacement is needed for a time because of transient adrenal insufficiency. When surgery fails, the disease recurs, or the patient is not a surgical candidate, drugs that suppress cortisol synthesis (such as osilodrostat, metyrapone or ketoconazole) are used; these control cortisol excess but do not shrink the tumor. In selected cases the pituitary-targeting agent pasireotide or a dopamine agonist as an adjunct may be used. When all options are exhausted, bilateral adrenalectomy provides definitive cortisol control but requires lifelong hormone replacement and carries a risk of Nelson's syndrome; radiotherapy may be applied for progressive disease.
Prognosis
Cushing's disease is caused by a benign tumor, but untreated cortisol excess markedly raises mortality through cardiovascular disease, infections and thromboembolic events. With effective control of cortisol excess these risks largely subside. Because recurrence can occur after surgery, lifelong follow-up is required, using urinary free cortisol, late-night salivary cortisol and pituitary MRI. Care is planned by a multidisciplinary team; outcomes vary from patient to patient and no outcome can be guaranteed.
참고 문헌
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:869.
- Winn HR, ed. Youmans Neurological Surgery. 6th ed. Saunders; 2011:1479.
- Asa SL, et al. Overview of the 2022 WHO Classification of Pituitary Tumors. Endocr Pathol. 2022.
- Fleseriu M, et al. Consensus on diagnosis and management of Cushing's disease: a guideline update. Lancet Diabetes Endocrinol. 2021.
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