Gonadotropin-Releasing Hormone and Organs of the Immune System

In this review, we address the physiological aspects of the gonadotropin-releasing hormone (GnRH) effects on the immune organs, such as red bone marrow, thymus, spleen, and lymph nodes. The use of GnRH drugs leads to the replacement of red bone marrow with yellow one and an increase in the content of lymphoid and myeloid progenitor cells. These processes are paralleled by osteoporosis due to increased bone resorption with changes in calcium metabolism and a decrease in the density of various bone tissues, although there are opposing reports that GnRH has no effect on bone density and calcium metabolism. GnRH affects the thymus during both embryonic development and postnatal ontogenesis, in inflammation and age-related involution. Not only does GnRH cause changes in the thymus, but the thymus may in turn influence the GnRH system. Although a direct impact of GnRH on splenic cells has not been detected, splenic mass changed due to active immunization against GnRH in experiment. Unfortunately, very few articles demonstrate the physiological mechanisms of immunomodulation in such conditions. In any case, the obvious insufficiency and inconsistency of publications on each aspect of GnRH effects indicate that they are still poorly understood, and it is worth furthering not only applied but also fundamental studies in this direction, particularly in the context of developing effective systems for immune control.