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Our bodies contain several organs that were once considered vestigial, such as the appendix, male nipples, and wisdom teeth. Until recently, the thymus gland was also thought to have little relevance beyond childhood. New evidence, however, overturns that view.
During many adult cardiothoracic operations, surgeons routinely remove the thymus (thymectomy). A team from Massachusetts General Hospital examined the outcomes of 1,146 patients who underwent thymectomy during heart or lung surgery, comparing them to a matched control group that had the same procedures without thymus removal.
The study, published in the August 2023 issue of the New England Journal of Medicine, found that five‑year mortality was 8.1 % in the thymectomy cohort versus 2.8 % in the control group. Cancer incidence over the same period was 7.4 % versus 3.7 %. These differences widened in subsequent follow‑up.
Senior author Dr. David T. Scadden stated, 'Our analysis demonstrates that the thymus is essential for long‑term health. Removing it doubles the risk of death and cancer, underscoring the need for careful consideration before performing a thymectomy.'
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The thymus sits just behind the sternum, between the lungs and anterior to the ascending aorta. This soft, pink‑gray gland is a key component of both the endocrine and lymphatic systems.
In the lymphatic system, the thymus educates T lymphocytes (T cells), guiding their maturation and releasing them into circulation. It also generates specific T and B cells that other organs cannot. Mature T cells patrol lymph nodes and peripheral tissues, defending against allergens, infections, and malignancies, while B cells help identify and neutralize harmful cells.
Within the endocrine system, the thymus secretes hormones such as thymulin, thymosin, and thymopoietin, which promote T‑cell development and modulate pituitary hormone release. It also produces hormones analogous to growth hormone, insulin, melatonin, and hormones involved in breast development.
The gland’s activity peaks during infancy and childhood, when it is largest. After puberty, thymic function gradually declines, and the organ shrinks, becoming largely fatty tissue in adults. This age‑related involution may have contributed to the historical belief that the thymus is of limited importance.
