INTERRELATIONS BETWEEN SEX HORMONE-BINDING GLOBULIN (SHBG), PLASMA-LIPOPROTEINS AND CARDIOVASCULAR RISK

The incidence of coronary artery disease is significantly higher in me n than in women, at least until menopause. This gender difference coul d be explained by the action of sex steroids on the lipoprotein profil e. In prepubertal children, high-density lipoprotein (HDL) cholesterol and triglyceride levels are similar between sexes, while adult men ha ve generally lower HDL cholesterol and higher triglyceride levels than premenopausal adult women. Most cross-sectional studies have reported that sex hormone binding globulin (SHBG) and testosterone levels corr elate positively with HDL cholesterol levels between sexes. Thus SHBG by modulating the balance in the biodisposal of testosterone and estra diol, might have a profound effect on the risk of cardiovascular disea se. However, adjustment for body weight and body fat distribution weak ens the association between SHBG, testosterone and HDL cholesterol. Th e negative correlation of fasting insulin with SHBG and HDL cholestero l levels in both sexes, and some evidence that insulin is an inhibitor of SHBG production in vitro, has suggested that hyperinsulinism might negatively regulate SHBG and HDL levels. It remains to be determined whether the inverse relationship between SHBG and insulin levels is co incidental or has a causal effect on the increase of atherosclerosis. Decreased SHBG has been shown to be predictive of the incidence of non -insulin-dependent diabetes mellitus in women but not in men, and of s ubsequent development of cardiovascular disease and overall mortality in postmenopausal women. SHBG is an index of androgenism in women and of insulin-resistance in both sexes, and might be useful in epidemiolo gical studies of cardiovascular risk. However, in men, SHBG is not pre dictive of the occurrence of cardiovascular disease. Whether SHBG migh t have an intrinsic protective effect on the arterial wall through SHB G-receptors is still highly speculative.