Plasma Variation of Corticosteroid-binding Globulin and Sex Hormone-binding Globulin

Abstract

Sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) circulate in plasma and bind their cognate ligands with high affinity, offering a steroid delivery system to target tissues by a variety of mechanisms. Analysis of these steroid-binding proteins is gaining importance in the clinical setting, although more information is warranted on their diurnal and biological variation. This study shows that plasma SHBG (in normal subjects) exhibits little diurnal or biological variation over the 30 day period studied, in contrast to CBG, where plasma levels peak in the early afternoon. This leads to attenuation of the diurnal free cortisol level rhythm compared to total cortisol. We also show that plasma CBG is significantly lower in male subjects with the metabolic syndrome compared to age-matched lean counterparts, and may therefore act as a surrogate marker of insulin resistance. The consequence of lower levels of CBG in these obese male subjects is reflected by higher levels of circulating free cortisol, potentially offering a more favourable environment for adipogenesis.

Sex Hormone–Binding Globulin and Risk of Clinical Diabetes in American Black, Hispanic, and Asian/Pacific Islander Postmenopausal Women

“…By reducing random within-person variation, multiple measurements of SHBG would have strengthened the observed association further. Also, SHBG is a stable protein with a relatively constant diurnal pattern, and its concentrations tend to be much more reliably measured than those of sex steroids (32, 33). Second, sample sizes were limited within racial/ ethnic groups.…”

Biosensor-based detection of reduced sex hormone-binding globulin binding capacities in response to growth-promoter administrations

“…The increased testing capacity would also improve the sensitivity of testing procedures allowing for the identification of suspect herds rather than isolated treated animals. The use of a SHBG-related parameter as a biomarker of growthpromoter abuse is promising due to the extended half-life of this glycoprotein and it's relatively stable circulating levels [31] even through stages of the bovine reproductive cycle [32]. Additional work will be required to determine the normal range of SHBG binding capacities in animals of various breeds, age and nutritional status, and who have been subjected to various forms of hormone administrations, so as to enable accurate identification of treated animals.…”

The Hypothalamic-Pituitary-Adrenal Axis, Obesity, and Chronic Stress Exposure: Sleep and the HPA Axis in Obesity

“…Only 5–10 % of cortisol circulates in active free form; cortisol binding globulin (CBG) binds most cortisol (80–90 %) with high affinity and 10–15 % is bound to albumin and sex-hormone binding globulin with lower affinity (Fig. 1) [11, 12]. CBG is fully saturated at cortisol levels over 500 nmol/l and also depicts diurnal variability, with a peak in the early afternoon [12, 13].…”

“…1) [11, 12]. CBG is fully saturated at cortisol levels over 500 nmol/l and also depicts diurnal variability, with a peak in the early afternoon [12, 13]. …”

“…In plasma, usually the total cortisol levels are measured and the unbound, protein-free fraction is indirectly estimated using the Coolens’ equation [12]. Measurements in saliva assess the biologically active, protein-free cortisol; hence the effects of within-subject changes or between-subject differences in CBG are eliminated.…”