Endocrine Abstracts

Introduction: The thyrotrophic effects of human chorionic gonadotrophin (HCG) are responsible for a physiological rise in fT4 and suppression of TSH in early pregnancy. Hyperthyroidism in this period is mostly due to gestational transient thyrotoxicosis (GTT) which is frequently mild and resolves spontaneously by 18 weeks, or due to Graves’ disease (GD) which would require closer monitoring through pregnancy (1). The pathophysiology of hyperemesis gravidarum is unclear, although it has been associated with higher HCG and fT4 levels. Here, a case of severe hyperemesis gravidarum (HG) presenting with features of thyroid storm is described.

Case: A 24 year-old primip with singleton pregnancy and no previous thyroid disease presented at 9 weeks gestation with a 3-week history of nausea, vomiting, anorexia, lethargy and 10% weight loss. Additional symptoms included palpitations and heat intolerance. Clinically, she was thin, dehydrated and anxious. She was afebrile, BP 110/76 mmHg with tachycardia at 150 per minute. Fine tremors were present. She had neither goitre nor other features of Graves’ disease. Hyperthyroidism was confirmed biochemically – fT4 50.6 pmol/l [Reference Interval (RI): 8–21 pmol/l], fT3 14.6 pmol/l [RI 3.5–6.0 pmol/l], TSH 0.01 mIU/l [RI: 0.34–5.60 mIU/l]. LFT showed a mixed picture with bilirubin 3 times elevated and transaminases raised between 5 and 9 times. White cells count and erythrocyte sediment rates were normal. ECG showed T inversions. Burch-Wartofsky score was 50. She was supported with intravenous infusion and anti-emetic which stabilized her pulse to 120 per minute. In view overt clinical features of hyperthyroidism, carbimazole 30mg was given daily. Daily fT3 showed an improving trend and she was discharged on day 4 when fT4 31.4 pmol/l, fT3 8.6 pmol/l, TSH <0.01 mIU/l. Carbimazole was stopped 2 weeks later. Her thyroid antibodies eventually returned as negative. She delivered a healthy baby girl at term and post-partum thyroid tests were normal.

Discussion: While GTT is largely a benign condition, serious complications had been reported. Confident differentiation of GTT from GD relies on evidence of thyroid autoimmunity. Delaying definitive treatment while awaiting antibody testing results may expose the patient to adverse effects of hyperthyroidism. In cases with features of severe hyperthyroidism, a short course of ATD may be necessary to avoid further end-organ deterioration while maintaining close monitoring of thyroid levels to avoid over-treatment.

Reference: [1] Ide et al. Comparative frequency of four different types of pregnancy-associated thyrotoxicosis in a single thyroid centre. Thyroid Research (2017) 10:4.