Prevalance of gestational diabetes mellitus in patients with gestational transient thyrotoxicosis

To investigate prevalence of gestational diabetes mellitus (GDM) in patients with gestational transient thyroxicosis (GTT).

Fifty two patients with GTT and 100 age matched healthy pregnant women were included. Fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), LDL-cholesterol, HDL-cholesterol, triglyceride, thyrotrophin (TSH) and thyroid hormones were measured at thyrotoxic state in GTT patients and at 6-12th weeks of pregnancy in control group. Oral glucose tolerance test (OGTT) with 100 g glucose was performed and laboratory parameters were re-evaluated at 24-28th weeks of pregnancy in all subjects.

Mean age of patients with GTT was 28.46 ± 5.45 and control group was 27.78 ± 3.75(p = 0.085). Patients with GTT had significantly higher HbA1c, LDL-cholesterol and HDL-cholesterol at 6-12th weeks of pregnancy (p < 0.01, p < 0.01 and p = 0.034, respectively). TSH was negatively correlated with HbA1c and LDL-cholesterol in thyrotoxic state in GTT patients (r = -0.393, p < 0.001 and r = -0.293, p < 0.001, respectively). OGTT showed GDM in 7 (13.5%) GTT patients and 4 (4%) healthy pregnants (p = 0.047). HbA1c, LDL-cholesterol and HDL-cholesterol were higher in GTT patients compared to healthy pregnants also at 24-28th weeks of pregnancy (p < 0.001, p < 0.001 and p = 0.024).

Although GTT is known to be a transient state that can resolve spontaneously, it might have negative effect on carbohydrate metabolism like other causes of hyperthyroidism.