Vaccination reduces the risk of severe health consequences of coronavirus-19 (COVID-19) infection. We report two cases of new-onset Graves’ hyperthyroidism suspected to have been precipitated by recent Comirnaty, Pfizer COVID vaccination.
Case 1: A 30 year old woman presented with sweats, rapid palpitations and arthralgia of the upper and lower limb joints and 2 kgs of weight loss within 7 days after a third COVID vaccination. Thyroid function tests showed subclinical hyperthyroidism; TSH: <0.02 mIU/L, free T4: 16.6 pmol/l, and positive TSH receptor antibody: 4.0 U/L (<1.0), anti-thyroglobulin and thyroid peroxidase antibodies. Thyroid ultrasound showed thyroiditis and sub-centimetre nodules. Follow-up clinical picture is most consistent with mild Graves’ disease with persisting subclinical hyperthyroidism and positive TSH receptor antibody, without antithyroid medication. Whilst she has multiple sclerosis treated with alemtuzumab, this was more than 5 years ago and thyroid function had been normal before the COVID vaccine, making alemtuzumab less likely to be causative.
Case 2: A 57 year old woman developed rapid palpitations, diarrhoea, tremors and 15 kg of weight loss, 2 to 3 weeks after a fourth COVID vaccination. TSH was 0.01 mIU/l, free T4: >75 pmol/l, free T3: >30.8 pmol/L, thyroid stimulating immunoglobulin 3.39 IU/L (<0.55) and positive anti-thyroglobulin and thyroid peroxidase antibodies. Thyroid ultrasound showed thyromegaly, features of thyroiditis and a 7 mm nodule. Treatment was commenced with carbimazole and propranolol with improvement.
A number of cases of new-onset or relapsed Graves’ disease following COVID vaccination have been reported, with the mRNA vaccine Pfizer most commonly associated and median time to symptom onset after vaccination of 7 days (1).
Graves’ hyperthyroidism should be considered when hyperthyroid symptoms follow soon after COVID vaccination, particularly with the mRNA Pfizer vaccine.