Serum Test Allows Early Intervention for Gestational Diabetes

New research indicates that pregnant women who are destined to develop gestational diabetes mellitus (GDM) in the third trimester have low levels of sex hormone binding globulin (SHBG) in the first trimester.

Therefore testing for this plasma protein could, facilitate earlier interventions that may improve outcomes.

Dr. Ravi Thadhani, from Massachusetts General Hospital in Boston said that glucose tolerance testing–the gold standard for diagnosing GDM–requires fasting and is performed during the third trimester. Unfortunately, “there are really no successful interventions that alter the outcome of GDM once it has been diagnosed.”

If, however, “GDM could be predicted in the first trimester, then there might be time for interventions that would have a beneficial impact,” he said.

“Sex hormone binding globulin has been shown to be a good predictor of type II diabetes in the non-pregnant state…so we decided to see if it was also useful during pregnancy,” Dr. Thadhani explained. Unlike glucose tolerance testing, SHBG testing does not require fasting and can be performed during the first trimester, he added.

The current study involved 44 pregnant women who developed GDM in the third trimester and 94 women who did not. SHBG levels were measured in serum samples that were collected from both groups during the first trimester.

The authors’ findings are published in the July issue of the American Journal of Obstetrics and Gynecology.

The average SHBG level in the GDM group was 187 nmol/L, significantly lower than the level in the non-GDM group — 233 nmol/L (p < 0.01) — the researchers report. Moreover, the SHBG level remained an independent predictor of GDM after adjusting for a variety of potential confounders, such as body mass index, age, race, and blood pressure.

For every 50-nmol/L rise in SHBG levels, the authors found that the risk of GDM dropped by 31%.

This was a proof of principle study, so “we don’t have any figures for sensitivity or specificity,” Dr. Thadhani noted. Larger studies are currently in the works that will provide these figures, he added.
Am J Obstet Gynecol 2003;189:171-176.