Establishment of paediatric age-related reference intervals for serum prolactin to aid in the diagnosis of neurometabolic conditions affecting dopamine metabolism

Background: There are a number of inborn errors of dopamine biosynthesis for which prolactin measurement may be a useful screening tool. However, the interpretation of prolactin results is difficult as age-related paediatric reference intervals are scant especially in infancy. Methods: Serum prolactin reference intervals were calculated from the existing laboratory data using an indirect method, based on patients (n = 2369) attending a tertiary care hospital over a 10-year period. The data were log transformed and partitioned by age and sex. Results: The prolactin results for all age and sex stratifications show non-Gaussian distributions (P < 0.0001). There are apparent age-related differences for prolactin during the first year of life with prolactin declining sharply during the first year of life and continuing to decline until five years of age when the concentrations stabilize. The sex differences are small until 13-17 years of age when prolactin is higher in girls than in boys. Conclusions: This is the first published study to report age-related prolactin reference intervals spanning all paediatric age groups where the data are age partitioned in infants under one year of age using an 'indirect' approach. It is envisaged that these reference intervals will be used to aid in the selection of patients presenting with features of central dopamine deficiency for lumbar puncture. Also, these reference intervals have the potential for treatment monitoring of patients with diagnoses of inborn errors of dopamine biosynthesis.