Assessment of prolactin secretion in children: a profile of circadian prolactin secretion and the principles for interpreting it

INTRODUCTION: Prolactin (Prl) is secreted in a circadian pattern, although no method of interpreting it has yet been established. The aim of the study was to assess Prl secretion in children on the basis of the Prl circadian profile and to establish principles for the interpretation of the results obtained by this method. MATERIAL AND METHODS: The analysis comprised 41 healthy short children (25 boys); aged 5.2-16.3 years, in whom hormonal disorders and chronic diseases had been excluded. The children were divided into prepubertal or pubertal subgroups. Serum Prl concentrations were measured every 3 hours for 24 hours. To assess the rhythm the parameters of macroscopic analysis were calculated and receiver operating characteristic (ROC) analysis was performed. The group for comparison consisted of 30 children aged 8.9-17.2 years with hyperprolactinaemia. RESULTS: In each subgroup significantly higher Prl concentrations were observed at night than by day. No statistical differences were noticed between the groups regarding Prl concentrations at particular time points or parameter values during circadian Prl rhythm evaluation. In the group analysed weak correlations were found between age and Prl peak and trough levels. On the basis of ROC analysis criteria for the existence of normal circadian Prl rhythm in children were established. CONCLUSIONS: 1. The presence of normal circadian Prl rhythm is observed if at least one of the following three criteria is fulfilled: amplitude >1.8779; X(n)/X(d) ratio >1.685; regression index <-0.4107. 2. No interpretation in relation to sex, age and stage of puberty is necessary for the circadian prolactin secretion rhythm in children.