A selective serotonin reuptake inhibitor, fluoxetine hydrochloride, modulates the pulsatile release of prolactin in postmenopausal women

We investigated serotoninergic regulation of prolactin release in estrogen-withdrawn postmenopausal women by using a serotonin reuptake inhibitor. Subjects underwent frequent blood sampling after placebo (basal) or fluoxetine administration. Mean 24-hour serum prolactin concentrations increased significantly in response to fluoxetine. Objective pulse analysis revealed no change in prolactin pulse frequency with serotoninergic stimulation, but maximal serum prolactin peak heights increased significantly. Multiple-parameter deconvolution disclosed no change in prolactin half-life, but a significant increase in the total mass of prolactin secreted per 24 hours during fluoxetine administration. Cosinor analysis of the prolactin time series showed a significant increase in the circadian amplitude and mean without any change in the time of maximal concentration during treatment with fluoxetine. We conclude that short-term activation of the serotoninergic system in the absence of substantial estradiol and opiatergic tone significantly increases the secretion of prolactin in postmenopausal women.