Low testosterone levels may raise the risk of age-related functional disability, according to a recent study.

Australian researchers found that elderly men with low levels of testosterone or other sex hormones have twice the likelihood of having declining physical function over two years' time compared with their peers who have the highest hormone levels.

"We also found that increasing muscle weakness -- possibly due to decreasing testosterone concentration in the blood -- could explain most of this relationship," said Benjumin Hsu, the study's principal investigator and a PhD candidate at the University of Sydney.

Hsu added that although testosterone levels and the ability to perform self-care activities both decrease with age, it is unclear whether one or the other is a cause or an effect of aging, or if they are both due to a common third cause.

For the study, researchers collected data from more than 1,300 men ages 70 and older.

As a measure of their capacity to function independently, the men reported their ability to perform activities of daily living, such as walking, eating, getting dressed and personal hygiene. They also had blood tests that measured levels of important hormones, including their male hormones -- testosterone and dihydrotestosterone -- and two types of the female hormone estrogen (estradiol and estrone) that are present in men in lower amounts than in women. Also tested were measures of muscle strength: grip strength and the strength of their quadriceps muscles in the thigh.

Researchers found that the lower the level of testosterone or either of the estrogens, the higher the chance that the men had worse functional abilities at the two-year follow-up evaluation.

"Low testosterone, estradiol and estrone concentrations may be important contributors to, or biologic markers for, physical decline in older men, which impairs their independent living," Hsu said.

However, the relationship between lower reproductive hormones and functional decline did not remain statistically significant when either of the measures of muscle strength was added to the analysis, he noted.

"This study suggests that low testosterone in older men could lead to a decline in muscle strength, which might explain their increased risk of functional disability," Hsu said.

The findings were recently presented at a joint meeting of the International Society of Endocrinology and the Endocrine Society: ICE/ENDO 2014 in Chicago.