A recent study was conducted to investigate whether men with prediabetes are at an increased the risk of testosterone deficiency.[7] Furthermore, as prediabetes is closely linked to obesity and metabolic syndrome, both of which are associated with testosterone deficiency [8], this study also explored whether the relationship between prediabetes and testosterone deficiency, if present, is independent of these factors.[7]


This study included 1,306 men whose sex hormones was measured during a medical examination. Serum total testosterone and sex hormone-binding globulin were measured; free and bioavailable testosterone concentrations were calculated by Vermeulen's formula.[9]

Prediabetes was diagnosed if any of the following criteria was met:

1) fasting glucose 100-125 mg/dL (IFG),
2) two-hour postprandial glucose 140-199 mg/dL (IPG), or
3) HbA1c 5.7%-6.4%.

The definition was adopted from the recommendations of the American Diabetes Association (ADA).[10]
Study subjects who had their levels below these cut-off were considered normoglycemic and not at risk.

Diabetes was diagnosed if a study participant had a prior history of diabetes or if the glycemic variables for prediabetes reached the criteria for diabetes:

1) fasting glucose at or over 126 mg/dL
2) two-hour postprandial glucose at or over 200 mg/dL, or
3) HbA1c at or over 6.5%

The diagnosis of metabolic syndrome was based on the modified ATP III criteria], and a study participant was considered to have metabolic syndrome if any three of the following were met:

1) waist circumference over 90 cm
2) triglycerides over 150 mg/dL
3) high-density lipoprotein cholesterol below 40 mg/dL
4) blood pressure over 130/85 mmHg
5) fasting glucose over100 mg/dL

Low total testosterone was defined by total testosterone <300 ng/dL, and low free testosterone was defined by free testosterone <6 ng/dL.

Logistic regression was performed to obtain the odds ratios (OR) for subnormal total testosterone (<300 ng/dL) or free testosterone (<6 ng/dL) in prediabetic and diabetic men compared with normoglycemic individuals, while adjusting for age, BMI, waist circumference, and metabolic syndrome.

Normoglycemia, prediabetes, and diabetes were diagnosed in 44.2%, 41.6% and14.2% men, respectively.

The age-adjusted odds ratio for subnormal total testosterone was 1.87 (range 1.38-2.54) in prediabetic men and 2.38 (range 1.57-3.60) in diabetic patients.

The risk remained significant in all multivariate analyses that further adjusted for BMI (an obesity indicator), waist circumference, the number of metabolic syndrome components, and the metabolic syndrome itself.

After adjusting for the metabolic syndrome, the risk for low-T in prediabetic men equals that of diabetic patients.

Neither prediabetes nor diabetes was associated with subnormal free testosterone in multivariate analyses.

Comment and Conclusion
This study clearly shows that prediabetes, which afflicts a large number of US adults, almost doubles the risk in a man for having low-T, regardless of fat mass, body fat distribution, blood fats, HDL and blood pressure. 

Because of the great risk for testosterone deficiency in predibetic men, this study suggests that testosterone should be measured routinely in men with prediabetes, even if they aren't obese.



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