Sex differences in glucose levels: a consequence of physiology or methodological convenience? The Inter99 study.

Aims/hypothesis: We aimed to examine whether sex differences in fasting plasma glucose (FPG), 2 h post-OGTT plasma glucose (2hPG) and HbA(1c) could be explained by differences in body size and/or body composition between men and women in a general non-diabetic Danish population. Moreover, we aimed to study to what degree the newly suggested high-risk HbA(1c) criteria overlapped with the current OGTT-based criteria of glucose intolerance.
Methods: We used cross-sectional data from 6,006 non-diabetic men and women. HbA(1c) and FPG levels were measured and a 75 g OGTT was performed in all individuals. Height, weight and waist and hip circumferences were measured and BMI was calculated. Data were analysed in age-adjusted linear regression models.
Results: Men had higher FPG and HbA(1c) levels than women, and women had higher 2hPG levels than men. Sex differences in 2hPG levels were explained by differences in height and FPG levels, but sex differences in FPG or HbA(1c) levels were not explained by anthropometric measures. Among individuals with HbA(1c) in the high-risk range (6.0-6.5%), 73% had normal glucose tolerance.
Conclusions/interpretation: Sex differences in 2hPG levels after an OGTT may to some extent be a consequence of giving the same amount of glucose to individuals with different body size. In contrast, sex differences in FPG and HbA(1c) levels are likely to have a true physiological basis. In clinical practice, the HbA(1c) assay may be more convenient than the OGTT, but it is important to note that different populations are identified by the two methods.