Changes in circadian rhythm of prolactin in short children are dependent on growth hormone secretion.

INTRODUCTION AND OBJECTIVE Taking into consideration the common ontogenic origin of prolactin (Prl) and growth hormone (GH), the Prl circadian pattern was analysed in children with different degrees of GH deficiency (GHD). MATERIALS AND METHODS The analysis comprised 100 short children (31 girls and 69 boys), aged: 10.1±3.51 years. Based on maximal GH secretion (GHmax) during two stimulating tests multiple hormone deficiency (MPHD), severe isolated GHD (SIGHD), partial isolated GHD (PIGHD) or idiopathic short stature (ISS) were diagnosed. Non-inferential chronobiometry (macroscopic analysis) of the circadian Prl rhythm, based on serum Prl measured every 3 hours during 24 hours, was performed. In this analysis, mesor, the area under curve (AUC), peak and trough level, dispersion, mean nocturnal and diurnal concentration, night/day ratio, amplitude and regression index were estimated. RESULTS In the study group, the positive correlations between GHmax and Prl concentrations at 02:00 and at 05:00 were observed, as well as between GHmax and mesor, amplitude, mean nocturnal concentration, night/day ratio and AUC. The nocturnal rise of Prl secretion was blunted in 100% MPHD and 50% SIGHD children, whereas in most children with PIGHD and ISS, the circadian Prl rhythm was normal. CONCLUSIONS 1) In short children, the lower the concentration of GH is, the more blunted nocturnal Prl secretion becomes. 2) In the majority of MPHD and SIGHD children (but not PIGHD), the circadian Prl rhythm was disturbed; namely, reduced nocturnal Prl secretion was noticeable.