Standard threshold for low testosterone doesn’t apply to young men, study finds

The standard cut-off point for low testosterone levels may not be as accurate for men in their mid-forties and younger, reports a study in Journal of Urology.

Lead author Alex Zhu, DO, University of Michigan, Ann Arbor, commented: “Young men have a different testosterone reference range than older men. “Our findings suggest that we should use age-specific cut-offs when assessing testosterone levels in young men.”

Different thresholds for low testosterone in young men

Patients with testosterone deficiency have low levels of the male sex hormone testosterone, with associated symptoms such as decreased libido and erectile dysfunction. Testosterone deficiency is often considered a disease that affects elderly men. However, urologists are seeing more and more young men with concerns related to testosterone deficiency — often accompanied by less specific symptoms such as low energy and fatigue.

Diagnosing low testosterone in young men also poses other challenges. The standard cut-off point for low testosterone is 300 nanograms per deciliter (300 ng/dL). However, that threshold is based on studies of testosterone by old manand ignore the normal age-related decline in testosterone levels.

To develop an age-specific set of cut-off points, Dr. Zhu and colleagues from the University of Michigan’s Department of Urology analyzed data on nearly 1,500 men, ages 20 to 44, from one national health study (National Health and Nutrition Examination Survey or NHANES). The study excluded men above hormone therapy or those with a history of testicular cancer or an orchiectomy (removal of the testicle). Because testosterone levels fluctuate normally on a daily basis, the analysis used only morning testosterone measurements.

The testosterone level range was assessed in the five-year age groups. The middle third (one third) of the distribution of testosterone levels in each 5-year age group was defined as the normal range. Values ​​below this range are used to calculate age-specific thresholds for low testosterone levels.

As expected, testosterone levels decrease with age. The age-specific cut-off scores for low testosterone ranged from 409 ng/dL at ages 20 to 24 to 350 ng/dL at ages 40 to 44 — significantly higher than the standard cut-off score. Each additional year of age was associated with a decrease in testosterone levels of 4.3 ng/dL.

Moving away from ‘one size fits all’

According to the authors, the study provides “the first assessment of population-based benchmark testosterone levels for young men in the United States”. They note that their study reflects the racial/ethnic diversity of the U.S. population and does not exclude men with health conditions other than testicular cancer or prior orchiectomy. .

Dr Zhu and co-authors write: “In today’s age of personalized medicine, clinicians can use age-specific testosterone levels to assess young men rather than relying ‘one size fits all’ approach. They emphasize the need for further studies, including how to interpret age-specific thresholds in the context of testosterone deficiency symptoms. The researchers also note that age-specific limits may affect insurance policy—Which sometimes does not include testosterone therapy unless testosterone lower than the standard threshold of 300 ng/dL.