Women tend to have higher levels of hs-CRP than men, especially if total and abdominal fat mass is greater. Metabolic stress, insulin resistance, and leptin resistance in women may also contribute to higher levels.
Although many pertinent studies do not differentiate between ranges for women and men, some interesting research can shed light on some of the gender differences observed for C-reactive protein. At present, commercial labs Quest Diagnostics and Labcorp do not differentiate hs-CRP ranges for women and men and instead provide a single range for both. However, gender-specific ranges for hs-CRP are defined in medical continuing education literature, i.e. "the normal serum levels for hsCRP is less than 0.55 mg/L in men and less than 1.0 mg/L in women" (Pahwa 2022).
In general, levels of C-reactive protein (CRP) in women may be up to 30-50% higher in women than men (Lu 2017), especially in Western countries. Research suggests that higher CRP in women may be associated with increased fat mass, metabolic stress, and possibly leptin resistance (Qasim 2011, Oda 2006).
Higher levels of C-reactive protein (CRP) observed in women versus men are thought to be associated with higher levels of body fat. Adipose tissue acts as a endocrine organ and secretes IL-6 which promotes production of CRP in the liver. Evaluation of data from the Dallas Heart Study found that increased body fat, especially abdominal adiposity, was associated more strongly with increased CRP in women than men. Specifically, when fat mass exceeded 33 kg, CRP was higher in women then men. However, when fat mass was equivalent and less than 33 kg, CRP was lower in women than men (Khera 2009).
Risk of metabolic syndrome may be reflected in hs-CRP levels as well. A cut-off of 0.65 mg/L was recommended for identifying metabolic syndrome in a study of 179 Japanese men and 166 Japanese women. Researchers note that C-reactive protein levels in general are substantially lower in Japan compared to Western countries (Oda 2006).
The VIRGO study looked at the relationship between hs-CRP and health status following a major cardiovascular event in 2,219 individuals. Women under age 55 have a higher risk of morbidity and mortality following myocardial infarction than men of the same age. One study looked at hs-CRP levels in this group and found that women had significantly higher levels of hs-CRP (median of 3.4 mg/L) than men (median of 2.2 mg/L) one month following MI. However, this difference didn’t translate into health differences 12 months later once other health variables were taken into account. Women also had significantly higher levels of the inflammatory marker LPLA2. Compared to men in the study, women were more likely to be single, black, diabetic, obese, and have a history of congestive heart failure and stroke, though they were less likely to have dyslipidemia (Lu 2017).
One cross-sectional analysis investigating gender differences in levels of CRP and their relationship to CVD risk and T2DM status found that CRP levels were highest in diabetic women (median of 2.8 mg/L) and significantly higher in non-diabetic women (median 1.4 mg/L) versus non-diabetic men (median 1.1 mg/L). Diabetic men had a median CRP of 1.4 mg/L, the same as non-diabetic women. Researchers speculate that higher CRP in women may be a reflection of increased metabolic stress, adipose dysfunction, and insulin resistance in women, especially in those with established type 2 diabetes. Interestingly, men had significantly higher coronary artery calcium levels than women, and diabetics had significantly higher CAC than non-diabetics. Higher CAC is associated with greater subclinical atherosclerosis (Qasim 2011).
References
Khera, Amit et al. “Sex differences in the relationship between C-reactive protein and body fat.” The Journal of clinical endocrinology and metabolism vol. 94,9 (2009): 3251-8. doi:10.1210/jc.2008-2406
Lu, Yuan et al. “Sex Differences in Inflammatory Markers and Health Status Among Young Adults With Acute Myocardial Infarction: Results From the VIRGO (Variation in Recovery: Role of Gender on Outcomes of Young Acute Myocardial Infarction Patients) Study.” Circulation. Cardiovascular quality and outcomes vol. 10,2 (2017): e003470. doi:10.1161/CIRCOUTCOMES.116.003470
Oda, Eiji et al. “The optimal cut-off point of C-reactive protein as an optional component of metabolic syndrome in Japan.” Circulation journal : official journal of the Japanese Circulation Society vol. 70,4 (2006): 384-8. doi:10.1253/circj.70.384
Pahwa, Roma, et al. “Chronic Inflammation.” StatPearls, StatPearls Publishing, 8 August 2022
Qasim, Atif N et al. “Gender differences in the association of C-reactive protein with coronary artery calcium in type-2 diabetes.” Clinical endocrinology vol. 74,1 (2011): 44-50. doi:10.1111/j.1365-2265.2010.03879.x