When we aren’t using lab work to guide treatment, we are using it as a screening tool, to try and predict the future. We know that women with certain hormone imbalances are at risk for gestational diabetes, and now we have the ability to use simple lab tests, to help us determine who is at risk even before they get pregnant.
Sex Hormone Binding Globulin (SHBG) is a protein in the blood that binds and carries many of our sex hormones including estrogen and testosterone. It’s an essential part of good hormone balance, as it prevents ‘too much’ active hormone from being available in the blood, and keeps women from having too many testosterone-like symptoms such as hair growth and acne.
Women who have SHBG levels that are lower than ideal before pregnancy, or in their first trimester have a significant risk of progressing to gestational diabetes, which increases their risk of a high risk pregnancy, or unexpected treatments (forceps delivery, Caesarean, or other interventions).
Insulin, which is a blood sugar regulating hormone, rises with weight gain, polycystic ovaries, or poorer diet choices. Insulin prevents the liver from making adequate SHBG, which liberates hormones to their “free” state, and can cause hormonal symptoms in women. SHBG levels are therefore a good estimate for how impactful metabolism and insulin are on a woman’s hormone function, because the higher the insulin rises, the lower SHBG gets.
We have found by tracking women in their preconception months, as they achieve pregnancy, and as they progress through their trimesters, that SHBG may be one of the most sensitive ways for predicting future gestational diabetes; because of it’s close tie with insulin. Blood sugar itself (which is measured on your lab work as ‘fasting glucose’) is not a particularly accurate test, as most women’s bodies will compensate for many years with poor blood sugar regulation, by over producing insulin to balance blood sugar out.
What is important to note, is that the range for SHBG that is predictive of GD, falls within the “normal” range of this test, as reported by Ontario laboratories. SHBG is considered normal in women between 20 to 180 nmol/L, and yet, any reading below 50-6 almost guarantees that women will develop GD in their pregnancy, when we test them in the first trimester(1,2). When we follow women in pregnancy, even women with a test result of 90 nmol/L are at a greater risk (compared to women who tested above 120 nmol/L)(3)
If we can predict who will get GD, we can offer timely and effective treatment through nutrition counselling, and supplementation that has been shown to reduce the risk.
If you have PCOS, a BMI over 25, a strong family history of diabetes or have had GD in a previous pregnancy, schedule a pre-conception or prenatal visit with one of our doctors to discuss testing and treatment options. The earlier we support women at risk, the greater likelihood we have of avoiding a diagnosis of Gestational Diabetes.
- Veltman-Verhulst SM, van Haeften TW, Eijkemans MJC, de Valk HW, Fauser BCJM, Goverde AJ. Sex hormone-binding globulin concentrations before conception as a predictor for gestational diabetes in women with polycystic ovary syndrome. Hum Reprod. 2010 Dec;25(12):3123–8.
- Tawfeek MA, Alfadhli EM, Alayoubi AM, El-Beshbishy HA, Habib FA. Sex hormone binding globulin as a valuable biochemical marker in predicting gestational diabetes mellitus. BMC Womens Health [Internet]. 2017 Mar 9 [cited 2018 Oct 10];17. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5345161/
- Zhang T, Du T, Li W, Yang S, Liang W. Sex hormone-binding globulin levels during the first trimester may predict gestational diabetes mellitus development. Biomark Med. 2018 Mar;12(3):239–44.