RESPONSE OF SEX-HORMONE BINDING GLOBULIN AND INSULIN-LIKE GROWTH-FACTOR BINDING PROTEIN-1 TO AN ORAL GLUCOSE-TOLERANCE TEST IN OBESE WOMEN WITH POLYCYSTIC-OVARY-SYNDROME BEFORE AND AFTER CALORIE RESTRICTION
D. Hamiltonfairley et al., RESPONSE OF SEX-HORMONE BINDING GLOBULIN AND INSULIN-LIKE GROWTH-FACTOR BINDING PROTEIN-1 TO AN ORAL GLUCOSE-TOLERANCE TEST IN OBESE WOMEN WITH POLYCYSTIC-OVARY-SYNDROME BEFORE AND AFTER CALORIE RESTRICTION, Clinical endocrinology, 39(3), 1993, pp. 363-367
OBJECTIVE We determined the relationship of short-term changes in circ
ulating insulin concentrations, resulting from an oral glucose load, t
o those in both sex hormone binding globulin (SHBG) and insulin-like g
rowth factor binding protein 1 (IGFBP-1) and assessed the effect of a
short-term low calorie diet on the levels of SHBG and IGFBP-1 during a
n oral glucose tolerance test. DESIGN A within-group comparison of bio
chemical indices during an oral glucose tolerance test before and afte
r calorie restriction. PATIENTS AND METHODS Six obese women with polyc
ystic ovary syndrome with mean (SD) BMI 34.2 (3.4) kg/m2 were studied
before and after one month on a very low calorie diet (350 kcal/day; C
ambridge diet). Each subject was given a 75-g oral glucose load after
an overnight fast and blood samples were taken every 30 minutes for 3
hours. These were analysed for glucose, insulin, SHBG, and IGFBP-1. RE
SULTS All the women lost weight (range 1.7-9.5 kg). The SHBG concentra
tions did not change significantly during the oral glucose tolerance t
est but there was a highly significant decline in IGFBP-1 levels both
before (0 min, mean (SD) 27.3 (10.6); 180 min, 8.9 (4.2) mug/l) and af
ter (0 min, 28.4 (12.1); 180 min, 6.2 (2.1) mug/l, P < 0.001) dieting.
The sum of the SHBG concentrations during the test, however, was sign
ificantly lower prior (129.9 (40.5) nmol/l) to calorie restriction tha
n after (164.3 (70 6) nmol/l), whereas there was no significant effect
of dieting on the IGFBP-1 response to glucose. CONCLUSIONS The change
s in insulin and SHBG concentrations found after dieting have been con
firmed. SHBG levels, in contrast to IGFBP-1, do not change in response
to a short-term increase in insulin or glucose concentrations. The di
fference in the response of the two binding proteins may be explained
by differences in their half-lives in the circulation or the regulatio
n of mRNA for the peptides by insulin. This study confirms that insuli
n regulates both SHBG and IGFBP-1 but that there is a difference in th
e time course of the response of the two proteins to insulin.