When is a glucose tolerance test typically performed?

A glucose tolerance test (GTT) is primarily used to assess how well the body processes glucose and is commonly performed during pregnancy to screen for gestational diabetes. During pregnancy, hormonal changes can lead to insulin resistance, making it crucial to monitor blood glucose levels to ensure both maternal and fetal health. The GTT usually involves fasting overnight, followed by the consumption of a glucose-rich beverage, and subsequent blood tests to measure how effectively the body handles glucose over a specified period.

The other options do not accurately reflect the standard application of the glucose tolerance test. Annual physical exams typically involve general health screenings rather than specific tests for glucose tolerance. Assessing thyroid function usually requires different tests, like measuring levels of thyroid hormones, and does not involve a glucose tolerance test. While the GTT can indirectly provide insights into insulin resistance, its primary purpose is to diagnose conditions like gestational diabetes, making its use in that context particularly critical.