Diagnostic Utility of the Prolactin Decrease Rate in the Diagnosis of Mild Hyperprolactinemia

Background Previous studies have yielded conflicting findings on the routine use of serial prolactin (PRL) measurement in patients with inconsistent signs or symptoms of mild hyperprolactinemia (HP). Therefore, we aimed to evaluate the effectiveness of serial PRL measurement and a previously undefined parameter which is the PRL decrease rate (PDR) method in the diagnosis of mild HP and prolactinoma. Materials and methods The data obtained from medical charts of patients in the sample population included serial PRL values at 0 minute (min), 30 min, and 60 min as well as macroprolactinemia (mPRL) levels. PDR was defined as the ratio of the difference between the PRL levels at 0 min and 60 min to the PRL level at 0 min. Results We obtained referral PRL (rPRL) levels from the files of 221 of 268 patients referred for HP. Of those referred, 153 (69.2%) had mild HP. Of the 165 patients in the serial PRL measurement group, HP was detected in 76 (46.1%), and stress-induced PRL elevation was found in 24 (14.5%). Of the 101 patients in the single PRL measurement group, HP was detected in 72 (69.9%; p<0.001). Moreover, a PDR score of 38.1% had 99% specificity and 26% sensitivity in HP exclusion, and a PDR score of 20.6% had 100% specificity and 30% sensitivity in prolactinoma exclusion. Conclusion In cases where clinical findings are insufficient, the serial PRL measurement method combined with the PDR for the diagnosis of prolactinoma and HP appears to be more reliable than the single measurement method.