Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1053 page)

   Leptin production is strongly influenced by nutritional state. Overeating increases serum leptin concentrations by nearly 40% within 12 hours, long before any changes in body fat stores. Conversely, in both normal-weight and obese subjects, fasting reduces serum leptin concentrations by 60–70% in 48 hours.

LEUCINE AMINOPEPTIDASE

   Definition

   LAP is a proteolytic enzyme widely distributed in bacteria, plants, and animals with high activity in the duodenum, kidney, and liver.

   
Normal range:
1.0–3.3 U/mL.

   Use

   As a marker of hepatic and pancreatic carcinoma.

   As a marker of early tubular (renal) injury in diabetes and as an indicator of SLE activity.

   Parallels serum ALP except that

   LAP is usually normal in the presence of bone disease or malabsorption syndrome.

   LAP is a more sensitive indicator of choledocholithiasis and of liver metastases in anicteric patients.

   When serum LAP is increased, urine LAP is almost always increased, but when urine LAP is increased, serum LAP may have already returned to normal.

   Interpretation

Increased In

   Obstructive, space-occupying, or infiltrative lesions of the liver