PubMed · 7362177
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G G Rhoads. 1980. Hemoglobin A1c reproducibility.. https://doi.org/10.7326/0003-4819-92-4-574
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Overweight adults with impaired glucose tolerance have a 5-10% risk of developing diabetes per year, and insulin resistance is an important cause of progression to diabetes in these individuals. Weight loss has been shown to improve insulin sensitivity and prevent or delay progression to diabetes. According to recent studies, the improvement in insulin sensitivity that occurs with weight loss is closely linked to the reduction of visceral adipose tissue (VAT), the collection of intra-abdominal adipose depots that includes omental and intrahepatic fat. After controlling for BMI, whole body fat, and subcutaneous fat, only VAT is an independent predictor of endogenous insulin sensitivity and glucose tolerance before or after weight loss. This, in turn, suggests that reducing VAT is crucial to improving insulin sensitivity and preventing diabetes in high-risk individuals. Recombinant human growth hormone (GH) is a lipolytic drug that reduces total body, abdominal, and visceral fat in growth hormone-deficient (GHD) adults. Several studies have reported substantial reductions in VAT following GH treatment in this population. Like GHD adults, abdominally obese individuals have increased VAT, insulin resistance, and growth hormone levels that are below normal during continuous 24-h monitoring. These similarities have prompted a number of recent investigations in abdominally obese adults that reported significant reductions in truncal and visceral fat and an improvement in insulin sensitivity following prolonged GH administration. However, other studies have shown that insulin resistance and glucose concentrations transiently worsen during the first few weeks of GH treatment and that these deleterious effects can persist even after VAT reduction has occurred. Prior studies involving GH treatment were generally limited to adults who were normoglycemic at baseline. Less is known about the effects of GH in adults with impaired glucose tolerance or diabetes. The effects of GH used in conjunction with insulin sensitizers on glycemic control and VAT in patients with impaired glucose tolerance will be reviewed.
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OBJECTIVE: The objective of this study was to improve the reproducibility of the oral glucose tolerance test (OGTT). DESIGN: Ten patients were used to demonstrate the difference between proportional and projected values in an OGTT. A procedure that plots data points at their actual time of collection, producing an accurate graph, that can predict a proportional glucose value at the intersection of the curve with the two-hour specified collection time, was developed. The efficacy of this procedure was demonstrated by clinical trials on a second group of ten patients. SETTING: Hospital outpatient clinic for the first group of ten patients since heparin lock was not required; Columbia Medical Center, Ormond Beach, FL for the second group since heparin lock was required. PATIENTS: All subjects in the first group were referred to the clinic by their family physician for an OGTT. Subjects in the second group were selected to meet the following criteria: no overt symptoms of diabetes, but with at least two high risk factors for Type 2 diabetes. INTERVENTION: A glucose load was given to each patient after a fasting sample blood sugar was analyzed. MAIN OUTCOME MEASURES: The recommended OGTT procedure for obtaining accurate predicted proportional two hour plasma glucose (2hPG) values requires a three hour OGTT with 1/2 hourly mid-test samples. A sample collection form was used to record all pertinent aspects of the test, time of first swallow, amount ingested in five minutes and the exact times of sample collections. A digital clock, located in the phlebotomist's view, was used to accurately establish all time intervals, including zero time. RESULTS: The study demonstrated that inspection of the OGTT curve and calculated values provide additional useful information. It also identified five impaired glucose tolerance (IGT) subjects, one gestational diabetes mellitus (GDM) patient, thirteen normal subjects, and one flat curve. CONCLUSIONS: Accurate time intervals are not necessary since 2hPG can be accurately expressed as a predicted proportional value if the true intervals are recorded and used to calculate the glucose level at the desired time interval(s).