LIVER FUNCTION

The liver works as the body's filter, removing toxins from the blood, processing nutrients and regulating its metabolism. A range of factors, including fatty liver disease, infections and excessive alcohol consumption can prevent the liver from performing these functions and if left untreated, can lead to liver damage.¹ When the liver is inflamed or damaged, enzymes including alanine aminotransferase (ALT) and gamma glutamyl transferase (GGT) leak from the liver cells into the bloodstream. As a result, elevated levels of ALT and GGT in the bloodstream can indicate the presence of liver disease.

Cirrhosis and other diseases of liver were the 9th leading cause of death for Aboriginal and Torres Strait Islander people in 2012 and were the 23rd leading cause for non-Indigenous people. The age standardised death rate for these diseases were four times higher for Aboriginal and Torres Strait Islander people than for non-Indigenous people overall.²

Data source and definitions The National Aboriginal and Torres Strait Islander Health Measures Survey (NATSIHMS) measured the levels of two blood enzymes related to liver function: alanine aminotransferase (ALT) and gamma glutamyl transferase (GGT). While elevated levels for either test may indicate liver damage, they cannot diagnose the presence of liver disease. Abnormal liver function as measured by ALT is defined as: an ALT reading of greater than 40 U/L for males. an ALT reading of greater than 30 U/L for females. Abnormal liver function as measured by GGT is defined as: a GGT reading of greater than 50 U/L for males. a GGT reading of greater than 35 U/L for females.

ALANINE AMINOTRANSFERASE (ALT)

ALT is an enzyme found mainly in the liver that helps the liver metabolise food into energy. Elevated levels of ALT in the blood can occur when the liver is damaged or diseased.³

In 2012–13, 16.5% of Aboriginal and Torres Strait Islander adults had abnormal or elevated levels of ALT in their blood, with higher rates among men than women (19.9% compared with 13.3%). After taking age differences into account, Aboriginal and Torres Strait Islander people were around one and a half times as likely as non-Indigenous Australians to have high ALT levels (rate ratio of 1.4).

Elevated ALT was more common among Aboriginal and Torres Strait Islander people living in remote areas in 2012–13. Around one in five (21.8%) Aboriginal and Torres Strait Islander people in remote areas had abnormal ALT levels compared with around one in seven (15.0%) of those who lived in non-remote areas.

Aboriginal and Torres Strait Islander people were at a higher risk of liver disease than their non-Indigenous counterparts in some age groups, with the biggest difference for those aged 25–34 years (19.6% compared with 12.2%).

Excess body fat is recognised as a risk factor for liver disease.⁴ As was the case for non-Indigenous Australians, Aboriginal and Torres Strait Islander people who were obese were around three times as likely to have elevated ALT compared with those of normal weight or underweight (25.5% compared with 8.6%).⁵

High blood pressure was also associated with elevated ALT in 2012–13. Aboriginal and Torres Strait Islander people with high blood pressure were twice as likely to have abnormal ALT compared to those with normal blood pressure (26.1% and 13.7% respectively). The same pattern was apparent for non-Indigenous adults; however the relationship was less pronounced (13.1% who had high blood pressure also experienced elevated ALT compared with 10.3% who had normal blood pressure).

Overall, almost three in five Aboriginal and Torres Strait Islander people (58.9%) who had elevated ALT also had high levels of GGT. While Aboriginal and Torres Strait Islander people with abnormal ALT were almost twice as likely to have high triglycerides (40.3% compared with 21.7%), there was no clear association with any of the other chronic disease biomarkers except for anaemia.GAMMA GLUTAMYL TRANSFERASE (GGT)

The enzyme GGT is found in many tissues in the body. It exists in a relatively high concentration in the liver but is also found in the tissues of the kidneys, bile duct, pancreas, gallbladder, spleen, heart and brain. When any of these tissues are damaged or diseased, GGT leaks from the tissue into the bloodstream. High GGT levels may therefore be indicative of a broader range of conditions and not just liver disease.^6,7

In 2012–13, around one in four (23.4%) Aboriginal and Torres Strait Islander people had abnormal or elevated levels of GGT in their blood. After taking age differences of the populations into account, Aboriginal and Torres Strait Islander people were twice as likely as non-Indigenous Australians to have abnormal levels of GGT (rate ratio 2.1).

As was the case with ALT, the proportion of Aboriginal and Torres Strait Islander people with elevated GGT was higher in remote Australia than in non-remote Australia. Over one in three (35.0%) Aboriginal and Torres Strait Islander people in remote areas had elevated GGT compared to one in five (20.0%) in non-remote areas. However, unlike ALT, abnormal GGT rates were similar for both men and women (23.9% compared with 22.9%).

Overall, abnormal levels of GGT increased with age for both Aboriginal and Torres Strait Islander people and non-Indigenous people. However, the rate of one in every seven (14.6%) Aboriginal and Torres Strait Islander aged 18–24 years with abnormal GGT was not reached by non-Indigenous people until the age of 45–54 years (13.1%).


As was the case with ALT, rates of abnormal GGT were higher among those who were obese or who had high blood pressure. For example, around one in three (32.0%) people who were obese had abnormal GGT compared with around one in seven (13.5%) who were of normal weight or underweight. Likewise, one in three Aboriginal and Torres Strait Islander people with high blood pressure also had abnormal GGT (33.3%) compared to only one in five who did not have high blood pressure (20.6%). However, unlike ALT, GGT was also linked to smoking, with current smokers more likely to have abnormal GGT than those who had never smoked (27.8% and 19.7% respectively).

Aboriginal and Torres Strait Islander people with abnormal GGT were more likely to have indicators of other chronic conditions as well. This was particularly the case for triglycerides, where those with high GGT levels were more than twice as likely as those with normal GGT levels to have high triglycerides (47.7% compared with 18.0%). They were also more likely to have high total cholesterol (36.4% compared with 21.9%), diabetes (20.3% compared with 8.4%) and signs of kidney disease (27.7% compared with 14.8%).

For more information on ALT and GGT, see Tables 1, 3, 4, 5, 6 and 11 on the Downloads page of this publication.

ENDNOTES

1 Angulo, P and Lindor, KD, 2002, 'Non-alcoholic fatty liver disease', Journal of Gastroenterology and Hepatology, <http://www.gastrohep.com/conreports/bangkok/jghs2.pdf>,
2 Australian Bureau of Statistics, Mar 2014, 'Causes of Death, Australia, 2012', ABS cat. no. 3303.0, <https://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/3303.02012?OpenDocument>,
3 Schindhelm, RK, et al. 2006, 'Alanine aminotransferase as a marker of non-alcoholic fatty liver disease in relation to type 2 diabetes mellitus and cardiovascular disease', Diabetes/Metabolism Research and Reviews, <http://dare.ubvu.vu.nl/bitstream/handle/1871/13286/21810_Schindhelm_proefschrift_V3.pdf?sequence=1#page=95>,
4 Farrell, GC et al. 2006, 'Nonalcoholic fatty liver disease: From steatosis to cirrhosis', Hepatology, <http://onlinelibrary.wiley.com/doi/10.1002/hep.20973/full>,
5 Australian Bureau of Statistics, 2013, 4364.0.55.005 - Australian Health Survey: Biomedical Results for Chronic Diseases, 2011–12, <https://www.abs.gov.au/ausstats/abs@.nsf/Latestproducts/4364.0.55.005Main%20Features12011-12?opendocument&tabname=Summary&prodno=4364.0.55.005&issue=2011-12&num=&view=>,
6 Lee, DS, et al. 2007, 'Gamma Glutamyl Transferase and Metabolic Syndrome, Cardiovascular Disease, and Mortality Risk: The Framingham Heart Study', Arteriosclerosis, Thrombosis, and Vascular Biology, <http://atvb.ahajournals.org/content/27/1/127.full>,
7 Ruttman, E, et al. 2005, 'Gamma-Glutamyltransferase as a Risk Factor for Cardiovascular Disease Mortality: An Epidemiological Investigation in a Cohort of 163 944 Austrian Adults', Circulation: Journal of the American Heart Association, <http://circ.ahajournals.org/content/112/14/2130.full>, Back to top