Concentrations of sex-hormone-binding-globulin (SHBG) in a population of normal women: relationship to risk factors for breast cancer

Serum concentration of sex hormone-binding globulin in healthy volunteers and patients with breast cancer stratified by sex and age

The objective of the present study was to compare sex hormone-binding globulin (SHBG) levels according to sex (healthy male and female volunteers) and age to determine reference values. Serum SHBG expression levels in patients with breast cancer with different tumor burden states were also determined. A total of 109 samples were obtained from 34 patients in 3 different disease states (non-tumor, localized tumor and systemic metastasis) during follow-up. A sandwich ELISA was conducted to measure SHBG, cancer antigen (CA)15-3 and CA125 expression levels. Wilcoxon rank-sum tests were performed on non-normally distributed data and an unpaired t-test was used for normally distributed variables. SHBG expression levels were higher in females compared with males (P<0.0001). When SHBG expression levels were compared by sex, the difference was maintained in the age groups <30, 30–39 and ≥50 years, but not in the 40–49 years group. In males, SHBG expression levels increased until the age of 49 and then decreased (P=0.01). In females, SHBG expression levels exhibited a decreased trend until the age of 49 (P=0.66). In patients with breast cancer, the SHBG expression levels revealed a decreasing trend after the age of 50, which was different compared with the healthy females. There was a decreasing trend of SHBG expression levels from pre-menopause to post-menopause healthy volunteers (P=0.74). CA15-3 (r²=0.07; P=0.59) and CA 125 (r²=−0.18; P=0.17) levels did not exhibit any significant correlation with SHBG expression levels. There was a significant difference in the SHBG expression levels between male and female healthy volunteers. SHBG expression levels also revealed different patterns between healthy female volunteers and female patients with breast cancer ≥50 years of age. The present study demonstrated that SHBG does not have value as a biomarker, but different reference values according to age and sex may aid in predicting high-risk groups for hormone-dependent cancer and guide treatment direction for post-menopausal breast cancer.

Visceral obesity and breast cancer risk

BACKGROUND

The risk for breast cancer and the sex hormone abnormalities noted in breast cancer patients have been demonstrated in women with upper body fat obesity. The objective of this study was to determine if the visceral component of upper body fat obesity was correlated with breast cancer risk.

METHODS

A case-control study of 40 consecutively enrolled women with breast cancer and 40 community-based age, weight, and waist circumference-matched control subjects was conducted. The areas of visceral fat, subcutaneous fat, and total fat were measured using computed tomography at the L-4 vertebral body. Calculations of relative risk for breast cancer were based on these fat compartments.

RESULTS

Patients with breast cancer had a significantly greater visceral fat area (P = 0.01), visceral-to-total-fat area ratio (VT ratio) (P < 0.001) and significantly lower subcutaneous-to-visceral-fat area ratio (SV ratio) (P < 0.001) compared with the matched controls. The relative risk for breast cancer increased with increasing VT ratio (< or = 0.24 = 1.0; > 0.24 = 9.5) (P < 0.0001) and decreasing SV ratio (> or = 3.64 = 1.0; < 3.64 = 8.5) (P = 0.0002).

CONCLUSIONS

Visceral obesity, as assessed by computed tomography, was a significant risk factor for breast cancer in women matched for age, weight, and waist circumference. Comparing the VT ratio for both groups, breast cancer patients had 45% more visceral fat compared with matched control subjects.

Obesity, body fat distribution, and sex hormones in breast cancer patients

This study addresses the relationship between female sex hormones, obesity, body fat distribution, and breast cancer. Increasing obesity correlated with a progressive fall in sex hormone-binding globulin (SHBG) level and an increase in testosterone level. Premenopausal breast cancer patients were found to have significantly lower levels of SHBG compared with age-matched and weight-matched controls. This difference in SHBG level was not noted in postmenopausal breast cancer patients. The SHBG level decreased with increasing upper body fat localization in breast cancer patients and controls. This effect was more marked in breast cancer patients which may explain our earlier finding that women with upper body fat localization are at increased risk for developing breast cancer.