Clinical Characteristics and Pregnancy Outcomes of Thyrotoxicosis During Pregnancy: A Retrospective Observational Study.

Objectives: Thyrotoxicosis during pregnancy may be associated with adverse maternal and foetal outcomes; however, data comparing overt and subclinical thyrotoxicosis are limited. This study aimed to evaluate clinical characteristics, management, and pregnancy outcomes, and to explore associations with the achievement of euthyroidism in pregnant women with thyrotoxicosis. Methods: This retrospective study included 70 pregnant women diagnosed with thyrotoxicosis who presented to the outpatient clinics between 2022-2023. Patients were classified as having overt (n=34) or subclinical (n=36) thyrotoxicosis based on trimester-specific thyroid function tests. After excluding three patients with Graves' disease and one with a molar pregnancy, 31 overt and 35 subclinical gestational thyrotoxicosis patients were included in the analyses. Demographic features, clinical findings, biochemical parameters standardized as multiples of the upper limit of normal, treatment data, and pregnancy outcomes were obtained from medical records. Correlation analyses were performed to evaluate associations between gestational week and thyroid function tests. Results: The mean age was 29.6±5.3 years, and the mean GW at diagnosis was 10.7±3.0, with no significant differences between groups. At diagnosis, TSH was lower and fT4/fT3 higher in overt thyrotoxicosis compared to subclinical cases (p<0.05). Euthyroidism was achieved at a mean of 17.1±4.0 weeks, without significant group differences. Prior antithyroid drug therapy had been initiated in 18.2% of patients, mainly with PTU, with similar doses and treatment durations between groups. Pregnancy outcomes were available for 42 patients; 13 experienced complications (oligohydramnios, preterm delivery, pre-eclampsia, gestational diabetes, and intrauterine foetal death). Complication rates did not differ between groups, although anti-TPO positivity was more frequent among patients with complications (p=0.006). Correlation analyses showed that earlier gestational age at diagnosis was associated with higher thyroid hormone levels, while later achievement of euthyroidism correlated with lower TSH and higher peak fT3. Conclusion: Pregnancy outcomes were similar in overt and subclinical thyrotoxicosis. Gestational age at diagnosis was associated with thyroid hormone levels but not with maternal or foetal complications. Most patients achieved euthyroidism during pregnancy, and anti-TPO positivity was more common among those with pregnancy complications.