Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (678 page)

   Placental origin: appears at 16th–20th week of normal pregnancy, increases progressively to two times normal up to onset of labor, and disappears 3–6 days after delivery of placenta. ALP may be increased during complications of pregnancy (e.g., hypertension, preeclampsia, eclampsia, threatened abortion) but is difficult to interpret without serial determinations. It is lower in diabetic than in nondiabetic pregnancy.

   Intestinal origin: is a component in approximately 25% of normal sera; increases 2 hours after eating in persons with blood type B or O who are secretors of the H blood group. ALP has been reported to be increased in cirrhosis, various ulcerative diseases of the GI tract, severe malabsorption, chronic hemodialysis, and acute infarction of the intestine.

   Benign familial hyperphosphatasemia.

   Ectopic production by neoplasm (Regan isoenzyme) without involvement of the liver or bone (e.g., Hodgkin disease; cancer of the lung, breast, colon, or pancreas; highest incidence in ovary and cervical cancers).

   Vascular endothelium origin—some patients with myocardial, pulmonary, renal (one third of cases), or splenic infarction, usually after 7 days during the phase of organization.

   Hyperphosphatasia (liver and bone isoenzymes).

   Hyperthyroidism (liver and bone isoenzymes). Increased ALP alone in a chemical profile, especially with a decreased serum cholesterol and lymphocytosis, should suggest excess thyroid medication or hyperthyroidism.

   Primary hypophosphatemia (often increased).

   ALP isoenzyme determinations are not widely used clinically; heat inactivation may be more useful to distinguish bone from liver source of increased ALP (extremely Ninety percent heat-labile: bone, vascular endothelium, reticuloendothelial system; extremely 90% heat-stable: placenta, neoplasms; intermediate 60–80% heat stable: liver, intestine). Also differentiate by chemical inhibition (e.g.,
L
-phenylalanine) or use serum GGT, leucine aminopeptidase.

   Children—mostly bone; little or no liver or intestine.

   Adults—liver with little or no bone or intestine; after age 50, increasing amounts of bone.

Decreased In

   Hypothyroidism