Lithium toxicity precipitated by profound hypothyroidism

Many patients who have undergone surgical treatment for thyroid cancer are treated with postoperative radioactive iodine ablation. Thyroid hormone is generally stopped for several weeks prior to treatment. We report the case of a woman on long-standing treatment with lithium for bipolar disorder who, after 3 weeks of withdrawal from thyroid hormone, presented to the hospital with severe lithium toxicity. She required admission to the intensive care unit and was treated with hemodialysis and supportive care with resolution of her illness. In this patient, renal dysfunction associated with her hypothyroid state was likely the precipitating event leading to the lithium toxicity. We review the effect of hypothyroidism on renal function and the association of hypothyroidism with drug toxicities. This case illustrates the potential for hypothyroid-induced renal dysfunction to lead to adverse clinical consequences in patients taking medications cleared by the kidneys.