We describe a case of Graves’ disease (GD) with thyrotoxicosis, which developed after hypothyroidism following hemithyroidectomy for low-risk papillary thyroid carcinoma (PTC), the latter diagnosed in pregnancy. New onset Graves’ disease (GD) after hemithyroidectomy for thyroid carcinoma is rare with a reported incidence of 0.2%1,2.
A 31-year-old woman, 9 weeks gestation, presented with 10mm right TIRADS 4 nodule on ultrasound with TSH receptor antibody (TRAb) negative T3 thyrotoxicosis (Figure 1). Biopsy demonstrated follicular thyroid neoplasm with papillary like nuclear features. After multidisciplinary discussion, hemithyroidectomy with central neck dissection was performed at 17 weeks' gestation. Histopathology showed 15x1.2mm BRAF V600E positive PTC without lymphovascular invasion or lymph node involvement. Thyroxine was initiated post-operatively. The patient delivered at term. Seven months post-partum, due to decreasing thyroxine requirements, TRAb was repeated and found to be high leading to a diagnosis of GD. Thyroxine replacement was discontinued and carbimazole was initiated, which the patient continues to take 12 months post-commencement.
Our case demonstrates the rare occurrence of GD after hypothyroidism following hemithyroidectomy for thyroid carcinoma. The median time between surgery and GD has been found to be 3.3 years (0.2-8.2 years) but can occur more than a decade post-operatively2-4. Risk factors for GD post hemithyroidectomy include female sex, and pre-operative thyroid peroxidase and thyroglobulin antibody positivity2. One proposed theory suggests that thyroid follicular cells release autoantigens, triggering antigen presenting cells to initiate T-helper cell humoral response, leading to TRAb production. In this case, the patient’s anti-TG and anti-TPO was negative pre-operatively and the negative TRAb status prior to surgery supports de novo synthesis in the post-operative state.
Clinical vigilance is necessary for patients with decreasing thyroxine requirements after hemithyroidectomy for thyroid cancer, and re-assessment with TRAb is recommended.