Its regression has been linked to the reduction in immunosurveillance[3] and the rise of infectious disease and cancer incidence in the elderly (in some cases risk is inversely proportional to thymus size).
[12] The ability of the immune system to mount a strong protective response depends on the receptor diversity of naive T cells (TCR).
[13] Loss of thymic function and TCR diversity is thought to contribute to weaker immunosurveillance of the elderly, including increasing instances of diseases such as cancers, autoimmunity, and opportunistic infections.
[14] There is growing evidence that thymic involution is plastic and can be therapeutically halted or reversed in order to help boost the immune system.
[17][19][20] The thymus has also been shown to decrease during hibernation and, in frogs, change in size depending on the season, growing smaller in the winter.
[21] Studies on acute thymic involution may help in developing treatments for patients, who for example are unable to restore immune function after chemotherapy, ionizing radiation, or infections like HIV.
In other research the results of the Greg Fahy TRIIM trial showed clinically significant reversal of thymus involution after the administration of human growth hormone (HGH), Dehydroepiandrosterone (DHEA) and metformin.