GCT

What is GCT?
The glucose challenge test (GCT), also called the one-hour glucose tolerance test, measures your body’s response to sugar (glucose). This test is performed during pregnancy to screen for gestational diabetes (diabetes that develops during pregnancy). GCT can be done as early as your first prenatal visit if you’re at high risk of gestational diabetes due to obesity, a personal history of gestational diabetes, and a family history of diabetes. A blood sugar level of 140 mg/dL or higher might indicate gestational diabetes.

Most women who have gestational diabetes deliver healthy babies. However, without careful management, gestational diabetes can lead to various pregnancy complications such as high blood pressure, increased risk of having a baby with an excessive birth weight and chances of a C-section delivery.

Why is GCT done?
The Glucose Challenge Test is performed to:

Screen for high blood sugar in presence of risk factors for diabetes in pregnancy
Detect gestational diabetes

What does GCT Measure?
Glucose Challenge Test (GCT) – Obstetrical measures blood glucose level one hour after the administration of 50 gms of glucose solution.

Glucose is a simple sugar or monosaccharide which is the main source of energy for all the cells of the body, and the only energy source for the nervous system. Carbohydrates consumed in the diet are broken down in the body to their simplest form, glucose. It is absorbed by the intestines and transported by the blood to various organs. Glucose is subsequently utilized by cells of these organs to produce energy wherever necessary, and the excess is stored either as glycogen in the liver for short-term storage or in fat tissues as triglycerides for long-term storage. The uptake, utilization, and storage of glucose after it is absorbed in the intestines are facilitated by the hormone, insulin which is secreted by the pancreas. Insulin influences the transport of glucose to the organs requiring it, like the heart, brain, working muscles, etc. It also directs storage of excess glucose. The action of insulin reduces sugar levels in the blood.

After every meal, sugar levels increase in blood and insulin is secreted as a response to reduce sugar levels until it becomes normal. If glucose levels fall too low in blood, another pancreatic hormone called Glucagon is released. Glucagon directs the liver to convert stored glycogen into glucose and release it into the blood. The insulin and glucagon hormones create a feedback mechanism to keep blood glucose levels within the normal range. Imbalance in their activity can cause an excess or shortage of blood sugar.

The glucose challenge test measures the levels of glucose in the blood, one hour after the administration of a sugar solution (usually 50 gm glucose dissolved in about 300 ml water). This helps to determine whether the body is able to utilize or store glucose efficiently. Excess sugar in blood indicates it is not being utilized or stored. It is usually performed as a part of the panel of tests performed during pregnancy and can be performed at any time during pregnancy. It is also necessary to repeat the test at 24 to 28 weeks to detect gestational diabetes.