PITUITARY-THYROID AXIS AND IMMUNE-SYSTEM - A RECIPROCAL NEUROENDOCRINE-IMMUNE INTERACTION

A good body of experimental and clinical results has supported the exi stence of numerous reciprocal interactions among the nervous, endocrin e and immune systems. Increasing evidence has been accumulated in the last years on the interaction between pituitary-thyroid hormones and t he immune system on the basis of either the existence of receptors for thyreotropic and thyroid hormones on lymphocytes or the frequent immu ne alteration in physiological and pathological fluctuations of thyroi d hormones. The data were obtained either in animals with experimental ly induced hyper- or hypothyroidism or in humans with various hyperthy roid or hypothyroid situations. Conversely, immune-derived products su ch as lymphokines and monokines have been shown able to influence the pituitary-thyroid axis modulating either the thyroid hormone levels or the hormone/cytokine production by thyrocytes. The present paper aims at summarizing the data available on the existence of thyroid-immune interactions, and at analyzing the possible integration between pituit ary-thyroid hormones and immune factors in favoring the development an d maintenance of both thymic and peripheral immune efficiency. The rel evance of pituitary-thyroid-immune interactions is discussed for its i mplication in the ageing process.