Differences in postload plasma glucose levels between 100-g and 75-g oral glucose tolerance tests in normal pregnant women: a potential role of early insulin secretion.
OBJECTIVE
To demonstrate a role of early insulin secretion on plasma glucose levels after different amounts of oral glucose loads in pregnant women.


METHODS
Forty-one pregnant women with normal glucose tolerance according to the Carpenter and Coustan' s criteria and 25 non-pregnant women (control group) with normal glucose tolerance according to the World Health Organization criteria were enrolled. Each subject was randomly scheduled to perform both the 100-g and 75-g OGTT within a 1-week interval. Venous blood was drawn at fasting, 30-, 60-, 120-, and 180-minute intervals during both tests for determination of plasma glucose and serum insulin levels.


RESULTS
The mean (+/- SE) ages of the pregnant and control groups were 33.3 +/- 0.9 and 31.8 +/- 1.4 years, respectively. The mean gestational age at the time of performing OGTT of the pregnant group was 28.7 +/- 0.6 weeks. In the non-pregnant group, the plasma glucose concentrations were not different between 75-g and 100-g OGTT whereas the serum insulin levels at the 30 and 180 minutes of the 100-g OGTT were significantly higher than those of the 75-g OGT. In the pregnant group, both plasma glucose and serum insulin concentrations at the 120 and 180 minutes of the 100-g OGTT were significantly higher than those of the 75-g OGT.


CONCLUSIONS
The limited ability of early insulin secretion to increase when glucose load increased in the pregnant women could explain the high plasma glucose levels at 2 and 3 hours of 100-g OGTT compared to those of 75-g OGTT.
Department of Obstetrics and Gynaecology, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand. sokaranr@medicine.psu.ac.th
Karanrat
K
Soonthornpun
Supamai
S
Soonthornpun
Atchara
A
Thamprasit
Jiraporn
J
Aksonteing
D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D016022:Case-Control Studies; D005260:Female; D005865:Gestational Age; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D011247:Pregnancy; D012016:Reference Values; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin