Endocrine Abstracts

Lithium is commonly used for management of Bipolar disorders. Li-induced thyroid dysfunction, including hypothyroidism and goitre are the most prevalent while hyperthyroidism is very infrequent, mainly characterised by transient painless thyroiditis but it increases the propensity to thyroid autoimmunity in susceptible individuals. Thyroid profile, thyroid auto-antibodies, assessment of thyroid size should be performed among patients initiating lithium, at baseline and later annually.

Case: A 32-year-old gentleman was referred to Endocrinology for evaluation of thyrotoxicosis. He has a background history of Bipolar psychosis, on long term Li (Priadel MR tablet 800 mg nocte) for last 7 years. Over previous years (Feb 2016 to March 2022), his TSH levels remained normal along with Li levels in therapeutic range. Four months ago, his thyroid profile showed suppressed TSH with raised FT4 and FT3 (Table), was started on Carbimazole 20 mg daily by GP and referred to Endocrinology for further evaluation. 2 months later, when reviewed by Endocrinology, he reported some heat intolerance, occasional palpitations, shakiness and restlessness which he co-relates to happen during anxiety episodes. There were no peripheral signs of hyperthyroidism and thyroid was not palpable. Repeated thyroid profiles showed downtrend of FT4 and FT3 to normal; however, TSH remained suppressed at <0.01mU/lafter 7 weeks of treatment. He was advised to decrease Carbimazole to 10 mg daily. His anti-TPO and anti-TSH receptor antibodies came out to be negative. On further review 6 weeks later, he mentioned that he is not taking Carbimazole for last 6 weeks, despite that repeated profile showed hypothyroidism with raised TSH (13.1mU/l) and low FT4 (11.6 pmol/l). He was advised to stop Carbimazole. Thyroid uptake scan with technetium was arranged to rule out drug induced thyroiditis vs toxic adenoma. This patient likely have Li-induced transient thyroiditis, hyperthyroid phase followed by development of hypothyroidism. Should the hyperthyroid phase be treated or monitored with thyroid function testing? In Li-induced thyroiditis, regular follow up is recommended since majority develop hypothyroidism subsequently. No role for anti-thyroid drugs or RAI, thyroid function should be monitored every 4-8 weeks to confirm resolution of hyperthyroidism and to detect hypothyroidism.