The role of the thymus-hypothalamus-pituitary-gonadal axis in normal immune processes and autoimmunity.

Gonadal steroids play an important role in the development and regulation of the immune system. Their effects may be mediated through a thymus-hypothalamus-pituitary-gonadal axis. The thymus gland secretes factor(s), including thymosin beta 4, that affect the release of gonadotropin releasing hormone (GnRH). GnRH regulates the subsequent release of luteinizing hormone, thereby affecting early ovarian development. Thymic factors may be modulated by gonadal steroids. Studies indicate that levels of thymosin beta 4 decrease in postmenopausal and ovariectomized women. In diseases such as systemic lupus erythematosus, abnormal patterns of estrogen metabolism may affect thymic function and contribute to the etiology of the disease.