Alkaline phosphatase pregnancy levels

Human leukocytes possess alkaline phosphatase (L13, 03, RIO, T6, V3, V4) whose activity parallels the concentration of certain circulating steroids. Thus, during the menstrual cycle, the leukocyte alkaline phosphatase evidences a peak at midcycle corresponding to the higher estrogen level. In the later stages of pregnancy the enzyme level increases. Corti-coid hormones also exert an effect on leukocyte alkaline phosphatase. 

In general, it would seem that osteoblasts could not compare as a source of alkaline phosphatase with intestine or placenta. In pregnancy the level of alkaline phosphatase is rarely increased above 10 Bodansky or Shinowara units, and yet the placenta s microvilli, which are extremely rich in alkaline phosphatase, are directly immersed in the ample and efficient maternal blood supply (H3). In the nonpregnant individual, therefore, before hyperphosphatasemia can be attributed to bone it would appear necessary to evaluate the intestinal contribution that is evident as heat-sensitive non-LPSAP protein. 

In another experiment, membranes isolated from chick intestinal epithelial cells containing both a Ca-dependent alkaline phosphatase and the more abundant Mg-dependent alkaline phosphatase, which are critical for phosphate transport, that were treated with the steroid have been shown to stimulate activities of both the enzymes (Birge and Avioli 1981). Furthermore, the stimulation of phosphate uptake paralleled the increase in Ca-dependent alkaline phosphatase activity (Birge and Avioli 1981). In humans, low levels of circulating 25(OH)D3 in pregnancy are associated with reduced bone mass in the offspring (review by Earl et al. 2010), suggesting that 25(OH)D3 may possibly be involved in placental calcium (and phosphate) transport... 

Osteomalacia is most often seen during pregnancy and lactation and is characterized by osteoporosis, deformity and fracture of bones, and tetany. The concentration of calcium in serum is low, often less than 7 mg. per 100 ml., and the level of alkaline phosphatase is elevated above the usual adult value of 3 to 5 units. 

---