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Thymic hyperplasia as a source of ectopic ACTH production
1Department of Clinical and Molecular Endocrinology, Graduate School, Tokyo Medical and Dental University, Japan.
Endocrine Journal
|November 15, 2000
Summary
Ectopic ACTH syndrome was diagnosed in a patient whose thymic hyperplasia, specifically its lymphocytes, produced adrenocorticotropic hormone (ACTH). This finding suggests thymic lymphocytes as a potential source of ACTH-producing tumors.
Area of Science:
- Endocrinology
- Oncology
- Immunology
Background:
- Cushing's disease is characterized by excess cortisol production, often due to pituitary adenomas.
- Transsphenoidal surgery is a common treatment for pituitary-related Cushing's disease.
- Ectopic ACTH syndrome, caused by non-pituitary tumors producing ACTH, presents a diagnostic challenge.
Observation:
- A patient with suspected Cushing's disease, initially negative for pituitary abnormalities, developed hypercortisolism requiring adrenalectomy.
- Post-adrenalectomy, the patient exhibited skin hyperpigmentation and elevated plasma ACTH, with CT revealing a thymic mass.
- Resection of the benign thymic hyperplasia led to normalization of ACTH levels and resolution of hyperpigmentation.
Findings:
- Thymic tissue extract demonstrated high ACTH content, similar to ectopic ACTH-producing tumors.
- Proopiomelanocortin (POMC) transcripts were identified in lymphocytes within the thymic hyperplastic tissue.
- Lymphocytes in thymic hyperplasia were identified as the likely source of deregulated ACTH production.
Implications:
- This case highlights thymic hyperplasia, particularly its lymphocytes, as a potential cause of ectopic ACTH syndrome.
- The findings expand the differential diagnosis for ACTH-dependent Cushing's syndrome.
- Understanding lymphocyte-mediated ACTH production in thymic hyperplasia may inform future diagnostic and therapeutic strategies.