Endocrine aspects of paediatric rheumatic diseases

Compared to the now numerous studies on the endocrinology of rheumatic diseases in adults, only a small number of studies has been published on children with rheumatic diseases. Prolactin has been most extensively investigated, showing interesting parallels with the findings in adults with rheumatological diseases. Thus, analogous to adult RA most forms of JRA or JCA (with the exception of ANA-positive JRA with uveitis) appear to show, if anything, low to normal levels of prolactin. Since the prolactin levels in adult RA depend on the inflammatory activity, and the physiological prolactin secretion decreases in chronic stress (especially sleep disorders), these results are most likely to be explained as reactive non-specific mechanisms in the stress of the disease. However, specific mechanisms are also being discussed to explain the low prolactin levels in adult RA. The results of prolactin measurements in juvenile SLE, juvenile ankylosing spondylitis and ANA-positive JRA with a raised incidence of uveitis, contrast with this. These conditions sometimes show significantly higher prolactin levels compared to healthy controls. A correlation of the increase of prolactin concentration with the inflammatory activity has been described for juvenile ankylosing spondylitis. These results correlate well with those of adult forms such as diseases of the seronegative spondyloarthropathies type, SLE and iridocyclitis. Raised prolactin concentrations are also found in these diseases. The inflammation promoting and immunostimulatory effects of prolactin found especially in animal experiments are confirmed clinically in these diseases by reports of successful treatments with the prolactin inhibitor, bromocriptine. The results available up to now for human growth hormone in JRA and JCA tend to be comparable with the results for prolactin in these form of paediatric rheumatological diseases. Besides normal values above, all lowered concentrations are measured for this hormone. Apart from other non-specific factors, its diminished secretion is mainly determined by the inflammatory activity of the disease. Low levels of growth hormone are likely to be a significant factor in the growth retardation in children with inflammatory rheumatological diseases. Up to now, the small number of investigations on gonadotrophins and the sex hormones in juvenile SLE and various forms of JRA published have not as yet yielded unequivocal results. The endocrine aspects of paediatric rheumatological diseases are thus still incompletely elucidated. However, there are many promising avenues for further fruitful research in this field.