Interleukin-18 (IL18, also known as interferon-gamma inducing factor) is a protein which in humans is encoded by the IL18 gene. The protein encoded by this gene is a proinflammatory cytokine. Apart from its physiological role, IL-18 is also able to induce severe inflammatory reactions, which suggests its role in certain inflammatory disorders. Endometrial IL-18 receptor mRNA and the ratio of IL-18 binding protein to interleukin 18 are significantly increased in adenomyosis patients in comparison to normal people, indicating a role in its pathogenesis. IL-18 has been implicated as an inflammatory mediator of Hashimoto’s thyroiditis, the most common cause of autoimmune hypothyroidism. IL-18 is up regulated by interferon-gamma. IL-18 has also been found to increase the Alzheimer’s disease-associated amyloid-beta production in human neuron cells.