Clinical Enzymology: Alkaline Phosphatase (ALP)

The level of alkaline phosphatase (ALP) in the blood varies significantly based on age and gender. Specifically, ALP levels are generally higher in children, particularly boys, due to the presence of the bone isoenzyme.

After menopause, women experience a slight increase in their bone isoenzyme levels, which contributes to a rise in overall ALP levels.

During pregnancy, ALP levels significantly increase, typically two to three times the normal range. This rise is primarily attributed to the placental isoenzyme but also involves an increase in the bone isoenzyme.

Obese individuals often exhibit higher ALP levels, with an average increase of approximately 10%, compared to those with a normal BMI.

Certain medications, such as oral contraceptives and fibric acid derivatives, can influence ALP levels. Oral contraceptives tend to decrease ALP, while fibric acid derivatives reduce both total ALP and the liver isoenzyme.

A family of enzymes classified as hydrolases, primarily responsible for cleaving phosphate-containing compounds.

The most abundant type of ALP found in the blood, produced in various tissues like the liver, kidney, and bone.

The ALP isozyme found in the liver, attached to the surface of cells near bile ducts.

The ALP isozyme found in bone cells responsible for the formation of new bone.

The ALP isozyme found in intestinal cells, released into the intestine after consuming fatty foods.

A mineral that activates ALP activity, along with other divalent ions like Co2+ and Mn2+.

Substances that inhibit ALP activity, preventing it from functioning properly.

Inhibitors of ALP that include phosphate, borate, oxalate, and cyanide ions.

Alkaline phosphatase (ALP) is an enzyme found in various tissues like liver, bone, intestines, and placenta.

Different ALP forms exist, with varying origins and release mechanisms. For example, liver injury causes ALP synthesis to increase. Meanwhile, bile acids break down canalicular cell membranes, releasing ALP into the blood.

Normal serum typically shows one type of ALP, from liver or bone. However, hepatobiliary disease can lead to different ALP forms, both normal and those attached to lipoproteins.

The intestinal isoenzyme of ALP is released into the duodenum after a meal, entering lymphatic fluid.

ALP isoenzymes have varying half-lives, affecting their persistence in the blood. For example, intestinal ALP has a short half-life, while liver ALP lasts longer.

Day-to-day fluctuations in total ALP are normal, but bone ALP can vary significantly.

Increased ALP activity in serum typically originates from the liver or bone.

Biliary obstruction, whether extrahepatic or intrahepatic, triggers increased ALP synthesis by liver cells. Extrahepatic obstruction usually results in higher ALP levels compared to intrahepatic obstruction.

A blood test used to measure the activity of the enzyme acid phosphatase (ACP).

A group of enzymes that break down phosphate compounds., primarily found in the prostate, bones, and liver.

ACP levels are elevated in conditions affecting the prostate, such as prostate cancer and benign prostatic hyperplasia.

The enzyme produced in the prostate gland and responsible for the breakdown of phosphate compounds.

A faster and more reliable blood test for prostate cancer compared to ACP.

Prostatic ACP can be detected in the blood and urine. High levels are associated with prostate cancer.

Prostate enlargement that is not cancerous and can cause urinary problems.

An inflammatory condition in the prostate that can cause elevated ACP levels.

The optimal pH level for 5'-Nucleotidase (5NT) activity is between 6.6 and 7.0.

5NT is an enzyme that is ubiquitously found in the body, particularly in the liver and other tissues.

Elevated serum 5NT activity is a strong indicator of hepatobiliary disease, hinting at problems with bile secretion.

Increased 5NT activity can result from both extrahepatic factors (e.g., blockage outside the liver) and intrahepatic factors (e.g., cholestasis within the liver).

In cases of parenchymal cell damage, such as infectious hepatitis, serum 5NT levels are only moderately increased compared to other hepatobiliary conditions.

Measuring 5NT activity in addition to total ALP can help distinguish between different causes of elevated ALP, especially in hepatobiliary disease.

5NT is a useful diagnostic marker because its activity often increases when liver ALP is normal, suggesting underlying liver disease.

The normal range for 5NT activity in the blood is between 3 and 9 units per liter (U/L), and there is no difference between men and women.

Increased GGT activity is often associated with the presence of hepatobiliary disease, a condition affecting the liver and bile ducts. However, the enzyme's lack of specificity can limit its diagnostic value, making it difficult to pinpoint the exact cause of the liver problem.

GGT levels rise significantly in individuals with obstructive conditions within the liver or bile ducts (posthepatic), such as gallstones or tumors blocking bile flow, reaching 5 to 30 times the normal reference range.

Elevated GGT levels are seen in patients diagnosed with primary or secondary liver cancer (metastases), suggesting an obstruction within the liver due to tumor growth.

A moderate elevation of GGT, with levels 2-5 times the reference range, is typical in cases of viral hepatitis, indicating inflammation and damage to the liver.

Over 50% of individuals with NAFLD (non-alcoholic fatty liver disease) exhibit a moderate increase in GGT levels. These elevations, while usually small, can be fleeting and are also observed in cases of drug toxicity.

GGT levels can increase 5 to 15 times the normal range in acute or chronic pancreatitis, especially when the pancreas is also affected by blockage in the bile ducts.

Patients with alcoholic hepatitis, characterized by liver inflammation caused by excessive alcohol consumption, often exhibit high GGT levels. Additionally, heavy drinkers generally have elevated GGT, even without obvious liver disease.

GGT levels tend to rise with increasing body weight and obesity. Moreover, alcohol's impact on GGT is more pronounced in overweight or obese individuals.