N. Botwood et al., SEX HORMONE-BINDING GLOBULIN AND FEMALE REPRODUCTIVE FUNCTION, Journal of steroid biochemistry and molecular biology, 53(1-6), 1995, pp. 529-531
Although sex steroids have long been known to influence serum concentr
ations of SHBG, it is now recognized that nutritional factors may be m
ore important in the regulation of SHBG in women. Thus, SHBG concentra
tions are negatively correlated with body mass index (BMI) and, more p
articularly, to indices of central adiposity. Polycystic ovary syndrom
e (PCOS), the most common cause of anovulatory infertility, is associa
ted with truncal obesity, hyperandrogenism and hyperinsulinaemia. Ther
e is evidence that insulin may be the humoral mediator of the weight-d
ependent changes in SHBG. Serum SHBG concentrations are inversely corr
elated with both fasting and glucose-stimulated insulin levels, and in
sulin has been shown to have a direct inhibitory effect on SHBG synthe
sis and secretion by hepatocytes in culture. However, the interrelatio
nship of BMI, insulin and SHBG appears to be different in women with P
COS from that in normal subjects. The clinical importance of the weigh
t-related suppression of SHBG is illustrated by the finding of a great
er prevalence of hirsutism in obese women with PCOS compared with thei
r lean counterparts. Obese subjects with PCOS have similar total testo
sterone concentrations to lean PCO women but have lower SHBG and recip
rocally higher free testosterone levels. Calorie restriction results i
n reduction of serum insulin followed by an increase in SHBG and a fal
l in free testosterone but an isocaloric, low-fat diet has no signific
ant effect on SHBG concentrations. Weight reduction in obese, hyperand
rogenaemic women with PCO is an important approach to the management o
f both anovulation and hirsutism.