Different rebound rise in plasma prolactin during the postdopamine infusion phase in puerperal women and patients with pathological hyperprolactinemia

Dopamine infused at a rate of 4 micrograms/kg . min for 120 min induced at the end of the infusion period a clear-cut and similar suppression of circulating PRL levels in normal and puerperal women as well as in patients with hyperprolactinemia either due to a tumor or of unknown etiology. At the discontinuation of the infusion there was a marked PRL rebound above baseline levels in normal subjects and a rapid return to basal levels in subjects with pathological hyperprolactinemia. In contrast, there was no increase in plasma PRL in puerperal women, in whom PRL levels remained suppressed during the whole postinfusion period. The reason(s) for this pattern in puerperal women is presently unknown, although previous estrogen loading of the lactotropes during pregnancy may be involved.