In recent years there has been increasing evidence in the literature that pituitary hormones are capable of regulating the immune system. There is evidence to suggest that prolactin is an immunostimulatory hormone and that reduction of serum prolactin levels in experimental animals by hypothesectomy or treatment with bromocriptine will result in a degree of immunosuppression. This information has been applied to humans and two clinical studies have begun. Both of these are in early phase of patient recruitment. One study is a randomized trial between placebo and bromocriptine in recurrent anterior uveitis using the end point of the number of recurrences per year to determine whether bromocriptine is capable of regulating the immune system in these patients. The second trial focuses on the additive effects of cyclosporine plus bromocriptine in attempts to treat patients with posterior uveitis at lower doses of cyclosporine to reduce its concurrent renal toxicity while at the same time achieve an immunosuppressive effect. Cyclosporine and prolactin compete for binding sites on the lymphocyte. Further studies in human disease will hopefully elucidate other aspects of the neuroendocrine axis which can be utilized to regulate the immune system to treat autoimmune diseases.
