What’s causing an isolated GGT elevation in my patient with an abnormal alkaline phosphatase on her routine admission lab?

Although serum gamma-glutamyl transpeptidase or GGT is a very sensitive test for liver disease, especially of biliary origin, it’s by no means a very specific test. Besides the liver, GGT is found in the kidneys, pancreas, prostate, heart, brain, and seminal vesicles but not in bone (1-4).

 
Obesity, alcohol consumption and drugs are common causes of GGT elevation (2). As early as 1960s, elevated GGT was reported in such seemingly disparate conditions as diabetes mellitus, congestive heart failure, myocardial infarction, nephrotic syndrome and renal neoplasm (3). Nonalcoholic steatohepatitis, viral hepatitis, biliary obstruction, COPD, liver metastasis, drug-induced liver injury can all cause GGT elevation (1-4).

 
An isolated GGT does not necessarily indicate serious or progressive liver disease. That’s one reason it’s often not included in routine “liver panel” lab tests (1).

What to do when GGT is high but other liver panel tests such as ALT, AST, albumin, and bilirubin are normal? If your patient is at risk of acquired liver disease, then further workup may be necessary (eg, hepatitis B and C screening tests). Alcohol consumption should be queried. Don’t forget conditions associated with iron overload. If your patient is obese, diabetic or has elevated both lipids, an ultrasound of the liver to look for fatty liver should be considered. In the absence of risk factors, symptoms, or physical exam suggestive of liver disease, isolated GGT elevation should not require further investigation (1).

 
One good thing that may come out of finding an isolated elevated GGT is to encourage your patient to curb alcohol consumption or lose weight when indicated. But don’t rely on a normal GGT to rule out heavy alcohol consumption as it may miss 70% to 80% of cases (6)! 

 
Bonus Pearl: Did you know that GGT activity is thought to increase in alcohol use due to its role in maintaining intracellular glutathione, an anti-oxidant, at adequate levels to protect cells from oxidative stress caused by alcohol?

Liked this post? Download the app on your smart phone and sign up below to catch future pearls right into your inbox, all for free!

Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

References

1. Carey WD. How should a patient with an isolated GGT elevation be evaluated? Clev Clin J Med 2000;67:315-16. https://www.ncbi.nlm.nih.gov/pubmed/10832186
2. Newsome PN, Cramb R, Davison SM, et al. Guidelines on the management of abnormal liver blood tests. Gut 2018;67:6-19. https://gut.bmj.com/content/gutjnl/67/1/6.full.pdf
3. Whitfield JB, Pounder RE, Neale G, et al. Serum gamma-glutamyl transpeptidase activity in liver disease. Gut 1972;13:702-8. https://www.ncbi.nlm.nih.gov/pubmed/4404786
4. Tekin O, Uraldi C, Isik B, et al. Clinical importance of gamma glutamyltransferase in the Ankara-Pursaklar region of Turkey. Medscape General Medicine 2004;6(1):e16. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1140713/
5. Van Beek JHDA, de Moor MHM, Geels LM, et al. The association of alcohol intake with gamma-glutamyl transferase (GGT) levels:evidence for correlated genetic effects. Drug Alcohol Depend 2014;134:99-105. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3909645/

6. Bertholet N, Winter MR, Cheng DM, et al. How accurate are blood (or breath) tests for identifying self-reported heavy drinking among people with alcohol dependence? Alcohol and Alcoholism 2014;49:423-29. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4060735/pdf/agu016.pdf

What’s causing an isolated GGT elevation in my patient with an abnormal alkaline phosphatase on her routine admission lab?

My middle-aged patient with a history of mediastinal irradiation for Hodgkin’s lymphoma in his 20s now has moderate aortic regurgitation. Could his valvular disease be related to the radiation he received over 20 years ago?

Absolutely! Mediastinal irradiation is associated with several cardiac complications, including coronary artery disease, pericarditis, systolic or diastolic dysfunction and valvular disease. Valvular disease may occur in 2-37% of patients after mediastinal irradiation, is dose-dependent, and generally does not manifest until 10-20 years after the radiation exposure.1 Since mediastinal irradiation is common in young adults diagnosed with Hodgkin’s lymphoma, these complications may be seen in early middle-age or later.

Valvular retraction is usually the first radiation-induced valvular change, and most commonly leads to mitral and aortic valve regurgitation.2 This retraction tends to occur within 10 years of the radiation therapy, followed by fibrosis and calcification of the valves after 20 years.

Although the pathophysiology of radiation-induced valvular disease is not entirely understood, activation of fibrogenic growth factors (eg, tissue growth factor β1 and myofibroblasts) which promote the synthesis of collagen has been postulated.1 Additionally, irradiation of aortic interstitial cells has been shown to cause transformation to an osteogenic phenotype that produces bone morphogenic protein 2, osteopontin and alkaline phosphatase, all important factors in bone formation and possibly valvular calcification.3

Since radiation-induced heart disease is the most common cause of non-malignant morbidity and mortality in patients who have undergone mediastinal irradiation, some have recommended screening of asymptomatic patients for valvular disease every 5 years by echocardiography beginning 10 years after radiation therapy. 2  If an abnormality is found, the screening frequency should increase to every 2-3  years,  if the valvular abnormality is mild, or annually if the abnormality is moderate. For severe valvular abnormalities, the patients should be considered for valve replacement.

If you liked this post, sign up under MENU and get future pearls straight into your mailbox!

References

    1. Gujral DM, Lloyd G, Bhattacharyya S. Radiation-induced valvular heart disease. Heart 2016;102:269–276. https://heart.bmj.com/content/heartjnl/102/4/269.full.pdf
    2. Cuomo JR, Sharma GK, Conger PD, Weintraub NL. Novel concepts in radiation-induced cardiovascular disease. World J Cardiol. 2016; 8 (9):504-519. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5039353/
    3. Nadlonek NA, Weyant MJ, Yu JA, et al. Radiation induces osteogenesis in human aortic valve interstitial cells. J Thorac Cardiovasc Surg 2012;144:1466–70. doi:10.1016/j.jtcvs.2012.08.041 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3665422/

Contributed by Rachel Wallwork, MD, Mass General Hospital, Boston, MA

 

My middle-aged patient with a history of mediastinal irradiation for Hodgkin’s lymphoma in his 20s now has moderate aortic regurgitation. Could his valvular disease be related to the radiation he received over 20 years ago?