Maternal tachycardia in pregnancy: a masked presentation of hyperthyroidism?

Introduction. Hyperthyroidism occurs in 35–50 per 100,000 women aged 20–29 years annually. Pregnancy outcomes in hyperthyroid mothers depend heavily on metabolic control. This case report discusses a pregnant patient with Graves' disease who presented without the typical symptoms of hyperthyroidism or thyrotoxicosis. Case report. A 31-year-old multiparous woman (gravida 3, para 2) at 38 weeks of gestation was admitted to a tertiary care center in labor. She had previously visited the emergency room due to severe diarrhea, dehydration, and hyperthyroidism. The patient received regular antenatal care at an endocrine clinic, where she was treated with propylthiouracil and propranolol until her seventh month of pregnancy. Subsequent evaluations revealed normalized thyroxine (T4) and thyroid-stimulating hormone (TSH) levels; thus, the treatment was concluded. The patient underwent an uncomplicated vaginal delivery and was safely discharged. Discussion. The patient had no prior history of thyroid disorders. Her initial symptoms emerged at two months of gestation, presenting as vomiting, dehydration, tachycardia, and weight loss. While an initial diagnosis of dehydration seemed to explain the tachycardia, laboratory tests revealed low TSH and increased free T4 (fT4) levels, confirming hyperthyroidism despite the absence of classic physical signs. Implementing maternal thyroid disorder screening to prevent such complications align with similar initiatives in Indonesia, such as the Congenital Hypothyroidism Screening program. However, expert guidelines from the American Thyroid Association and the Endocrine Society do not currently recommend universal thyroid screening in the absence of specific risk factors. Conclusion. Optimal pregnancy outcomes in hyperthyroid patients require early diagnosis and adequate treatment. Tachycardia presenting during early pregnancy should be investigated for underlying causes other than dehydration. Although universal thyroid screening in early pregnancy is not recommended without risk factors, strong clinical suspicion remains a clear indication for further laboratory examination.