Summary
Factors influencing sex-hormone binding globulin (SHBG) concentrations in obesity
are poorly understood. Preliminary observations suggest that dietary lipids may be
involved and there are data confirming a direct inhibiting effect of insulin. Since
only some obese subjects show lowered SHBG levels, we performed this study with the
aim of defining obese women with low SHBG (LSO) (2 SD above normal values) in comparison
with those presenting normal globulin concentrations (NSO). These groups were selected
from a larger group of obese women with a history of normal menses and aged less than
40 years. An age-matched group of normal weight healthy women served as controls.
Both LSO and NSO had similar body mass index and percentage body fat, but the waist
to hip girth ratio (WHR), an index of body fat distribution, was significantly higher
in LSO (0.88 ± 0.04) than in NSO (0.81 ± 0.09; P < 0.05). Gonadotropin and androgen
concentrations were similar in both groups, whereas estrone (E1) levels were higher
in LSO (32.8 ± 15.8 pg/ml) than in NSO (19.4 ± 6.2 pg/ml; P < 0.05; controls: 23.5
± 7.8 pg/ml; P < 0.05). Moreover, compared to NSO, LSO women had significantly higher
glucose-stimulated insulin and C-peptide levels. Partial regression analysis revealed
significant correlation coefficients between SHBG, stimulated insulin values (r =
-0.38; P < 0.05) and WHR (r = -0.40; P < 0.05). Therefore, compared to NSO, LSO women
have distinctive clinical and endocrine characteristics, namely more pronounced hyperinsulinemia,
higher E1 concentrations and a central type body fat distribution.
Key words
Obesity - Sex Hormone-Binding Globulin - Body Fat distribution - Sex Hormones - Insulin
