Hyperthyroidism induces glucose intolerance by lowering both insulin secretion and peripheral insulin sensitivity.
OBJECTIVE
The objectives of this study were to examine the effects of hyperthyroidism on glucose tolerance, insulin secretion, and insulin sensitivity.


METHODS
Thirty-eight patients with hyperthyroidism and twenty-six healthy volunteers with matching age and body mass index were included. Patients with conditions known to affect glucose metabolism were excluded. An oral glucose tolerance test was performed after the diagnosis of hyperthyroidism and again when they achieved euthyroid state. Areas under the glucose and insulin curves were used to assess plasma glucose and insulin responses, respectively. Beta-cell function was determined by the corrected insulin response (CIR) and homostatic model assessment model 2 (HOMA2-%B). Peripheral insulin sensitivity was determined by the insulin activity (IA) and HOMA2-%S.


RESULTS
The prevalence of glucose intolerance in hyperthyroid state was 39.4% [impaired glucose tolerance (IGT) 31.5% and diabetes mellitus (DM) 7.9%]. This was significantly higher than that of 30.7% [IGT 19.2% and DM 11.5%] in healthy volunteers (p < 0.05). Glucose intolerance was associated with higher systolic blood pressure, higher mean arterial pressure, lower CIR, and higher T4 levels but not with the levels of T3. IA and HOMA2-%S significantly improved when achieving a euthyroid state despite the increase in body mass index.


CONCLUSIONS
In conclusion, glucose intolerance is common in hyperthyroidism. Both impaired insulin secretion and decreased peripheral insulin sensitivity are the factors contributing to the development of abnormal glucose tolerance in the hyperthyroid state.
Roubsanthisuk
Weranuj
W
Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Watanakejorn
Praneet
P
Tunlakit
Monchaya
M
Sriussadaporn
Sutin
S
D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D003920:Diabetes Mellitus / Q000453:epidemiology / Q000209:etiology; D005260:Female; D018149:Glucose Intolerance / Q000453:epidemiology / Q000209:etiology*; D005951:Glucose Tolerance Test; D006801:Humans; D006980:Hyperthyroidism / Q000150:complications*; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D000078790:Insulin Secretion; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D013785:Thailand / Q000453:epidemiology
D007328:Insulin