Prolactin Secretion in Healthy Adults Is Determined by Gender, Age and Body Mass Index

BACKGROUND: Prolactin (PRL) secretion is quantifiable as mean, peak and nadir PRL concentrations, degree of irregularity (ApEn, approximate entropy) and spikiness (brief staccato-like fluctuations). HYPOTHESIS: Distinct PRL dynamics reflect relatively distinct (combinations of) subject variables, such as gender, age, and BMI. LOCATION: Clinical Research Unit. SUBJECTS: Seventy-four healthy adults aged 22–77 yr (41 women and 33 men), with BMI 18.3–39.4 kg/m(2). MEASURES: Immunofluorometric PRL assay of 10-min samples collected for 24 hours. RESULTS: Mean 24-h PRL concentration correlated jointly with gender (P<0.0001) and BMI (P = 0.01), but not with age (overall R(2) = 0.308, P<0.0001). Nadir PRL concentration correlated with gender only (P = 0.017) and peak PRL with gender (P<0.001) and negatively with age (P<0.003), overall R(2) = 0.325, P<0.0001. Forward-selection multivariate regression of PRL deconvolution results demonstrated that basal (nonpulsatile) PRL secretion tended to be associated with BMI (R(2) = 0.058, P = 0.03), pulsatile secretion with gender (R(2) = 0.152, P = 0.003), and total secretion with gender and BMI (R(2) = 0.204, P<0.0001). Pulse mass was associated with gender (P = 0.001) and with a negative tendency to age (P = 0.038). In male subjects older than 50 yr (but not in women) approximate entropy was increased (0.942±0.301 vs. 1.258±0.267, P = 0.007) compared with younger men, as well as spikiness (0.363±0.122 vs. 0463±2.12, P = 0.031). Cosinor analysis disclosed higher mesor and amplitude in females than in men, but the acrophase was gender-independent. The acrophase was determined by age and BMI (R(2) = 0.186, P = 0.001). CONCLUSION: In healthy adults, selective combinations of gender, age, and BMI specify distinct PRL dynamics, thus requiring balanced representation of these variables in comparative PRL studies.