Endocrine Abstracts

Hypothyroidism has been a common side effect of newer antineoplastic agents used for non-thyroid cancer treatment including tyrosine kinase inhibitors, bexarotene, Ipilimumab etc. However, we have not had any case reported with hypothyroidism following the treatment with Paclitaxel and Carboplatin in patient with non-thyroid cancer treatment. There has been the earlier onset and higher incidence of hypothyroidism observed in concomitant therapy with paclitaxel and radiation as compared with radiation alone in treatment of locally advanced head and neck cancer. A 64-year-old lady with known metastatic breast cancer to bone, omentum, right pleural and right sided pleural effusion with suspected malignant cells was started on the chemotherapy regime of Paclitaxel followed by Carboplatin: Paclitaxel cycles initiated in April 2024 followed by Carboplatin in August 2024. She had normal thyroid function test: TSH 3.10 mU/l, free T4 14.3 pmol/l in November 2023 prior to the start of the chemotherapy. She presented to the emergency department with generally unwell, loose stool, slurred speech, and generalised weakness in October 2024. She was found to have bradycardic at 42 beats per minute and marked hypothyroidism: TSH 37.85 mU/L and free T4 <5.4 pmol/l. She was found to have small right cerebellar enhancing lesion on CT head during admission, in addition to her progressive disease on recent CT scan in June 2024. Her heart rate appeared to vary between 35 to 71 and stable blood pressure prior to the start of liothyronine 10 micrograms twice daily. She was subsequently put on palliative with her progressive metastasis disease, extreme frailty a few days following admission and had passed away peacefully. This case highlights that hypothyroidism could be the potential side effect of Paclitaxel and Carboplatin chemotherapy and would be beneficial for the patient to have monitored the thyroid function test during treatment.