Sex hormone-binding globulin, testosterone and type 2 diabetes risk in middle-aged African women: exploring the impact of HIV and menopause
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Objectives
Sex hormone-binding globulin (SHBG) and testosterone are differentially associated with type 2 diabetes (T2D) risk. We investigated whether these associations differ by HIV and menopausal status in Black South African women living with (WLWH) and without HIV (WLWOH).
Design
Cross-sectional observational.
Methods
Eighty one premenopausal (57 WLWOH, 24 WLWH) and 280 postmenopausal (236 WLWOH, 44 WLWH) women from the Middle-Aged Soweto Cohort (MASC) completed the following measures: circulating SHBG and sex hormones, body composition (dual energy x-ray absorptiometry), oral glucose tolerance test to estimate insulin sensitivity (Matsuda index), secretion (insulinogenic index, IGI) and clearance, and beta-cell function (disposition index, DI). Dysglycaemia was defined as either impaired fasting or postprandial glucose or T2D.
Results
SHBG was higher and total and free testosterone were lower in postmenopausal WLWH than WLWOH (all p < 0.023). Irrespective of HIV serostatus, SHBG was positively associated with Matsuda index, insulin clearance and DI and inversely with HOMA-IR (all p<0.011). The association between SHBG and Matsuda index was stronger in premenopausal than postmenopausal women (p=0.043 for interaction). Free testosterone (and not total testosterone) was only negatively associated with basal insulin clearance (p=0.021), and positively associated with HOMA-IR in premenopausal and not post-menopausal women (p=0.015 for interaction).
Conclusions
We show for the first time that midlife African WLWH have higher SHBG and lower total and free testosterone than WLWOH, which corresponded to their higher beta-cell function, suggesting a putative protective effect of SHBG on T2D risk in WLWH.
Significance statement
This study in midlife Black African women suggest that higher sex hormone binding protein (SHBG) and lower free testosterone in women living with HIV (WLWH) may be associated with reduced risk of type 2 diabetes (T2D) compared to women living without HIV. Further, this study provides a putative mechanism underlying the lower prevalence of T2D in WLWH and obesity compared to women living with obesity but without HIV. However, longitudinal studies are required to understand the clinical implications of these findings.
