Hyperprolactinemia diagnostics--dilemmas over optimal selection of prolactinemia time points

Laboratory discrimination of pathologic hyperprolactinemia is an important step in the diagnosis of pathology influencing overall health and fertility. A major issue is the choice of time and circumstances for obtaining a blood sample for prolactin assay that would be representative for mean daily plasma concentration of a subject.

The aim of the study was a comparison of reliability of single prolactin assessment on various time-points in a day with circadian prolactinemia profile in order to find the easiest, the least expensive, and the most reliable method of hyperprolactinemia diagnosis.

The study was a retrospective analysis of 138 women, hospitalized in the Department of Endocrinology and Metabolic Diseases, Polish Mother`s Memorial Hospital - Research Institute, Lodz, Poland, in whom the circadian profile of prolactin (including assays at 8.00 am, 11.00 am, 2.00 pm, 5.00 pm, 8.00 pm, 11.00 pm, 2.00 am, 5.00 am and repeatedly at 8.00 am) had been assessed.

On the basis of AUC (area under the curve) of prolactin concentrations, hyperprolactinemia was diagnosed in 34 subjects (24.6 % of the entire group). The attempts to diagnose hyperprolactinemia based on a single prolactin assay failed due to a high percentage of false negative and false positive results. Only significant hyperprolactinemia with mean prolactin concentration of about 100 µg/l or more appeared easy to diagnose. Combinations of several time points also appeared not reliable enough.

The nine-point daily profile of prolactinemia in any patient with clinical suspicion of hyperprolactinemia seems the best mode for estimating mean circadian prolactin concentration.