A 33-year-old woman, who was 9 weeks into her first pregnancy, was admitted with prolonged vomiting and secondary dehydration. She had lost 6 kg in weight since becoming pregnant. There was a strong family history of thyroid disease: two sisters were hypothyroid and one brother had required radioactive iodine for Graves’ disease.
On examination, she had a smooth, small goitre. Her pulse was 94 beats per minute and her blood pressure was 104/42 mmHg. There was a tremor of the outstretched hands. Urinalysis was normal.
Investigations:
-serum sodium143 mmol/L (137–144) serum potassium4.4 mmol/L (3.5–4.9) serum creatinine105 µmol/L (60–110)
-serum thyroid-stimulating hormone (TSH)<0.01 mU/L (0.4–5.0) serum free T424.0 pmol/L (10.0–22.0)
-serum free T311.0 pmol/L (3.0–7.0)
A TSH receptor antibody concentration was awaited.
In addition to rehydration, what is the most appropriate next step in the management of her abnormal thyroid function?
- carbimazole
- labetalol
- observation
- propranolol
- propylthiouracil