Extremely High Isolated Maternal Alkaline Phosphatase Serum Concentration -2 Case Reports

Alkaline phosphatises (ALP) are a group of isoenzymes produced by liver (isoenzymes ALP1-1), bones (isoenzymes ALP2), kidneys, small intestine and placenta (isoenzymes ALP-3) [1,2]. The serum ALP level represents the total amounts of isoenzymes that are released from the tissues into the bloodstream. Placenta ALP is physiologically produced by placenta at the brush border membranes of the syncytiotrophoblast, and its’ major function is thought to aid in metabolism and facilitate transport across cell membranes [3]. It appears in maternal serum between the 15th and the 26th weeks and increases during the third trimester. Usually, ALP production in maternal serum is not major and total serum ALP level remains normal. The mechanism of serum placental ALP increase is not well understood. In postpartum period, ALP isoenzyme activity decreases to the normal level at about 20 weeks after delivery. Marked elevation of serum ALP may be caused by liver or bone pathology such as malignancy, extra hepatic biliary obstruction, and intrahepatic cholestasis [2]. We report 2 cases of markedly elevated placental isoenzymes of ALP in the third trimester in otherwise uncomplicated pregnancies. In both cases, serum ALP returned to normal level after delivery.