Introduction: Levothyroxine is the most prescribed medication in the last decade in the United States and used commonly for treatment of hypothyroidism. Despite this, overdoses with levothyroxine are rare. Patient presentations can range from asymptomatic with a benign course to severe thyrotoxicosis. Here we present a case of an elderly woman with depression and prior suicide attempts who ingested an estimated 3000 mcg of levothyroxine in a suicide attempt.
Case Description: An 86-year-old female with history of hypothyroidism, major depression, bipolar disorder, mild cognitive impairment, multiple prior suicide attempts presented to the hospital 3 hours after intentional ingestion of 3000 mcg of levothyroxine. She denied co-ingestion of other medications. On physical examination, she had blood pressure of 139/76 mmHg, heart rate of 67 beats per minute (bpm), temperature 98.6°C, respiratory rate 18 breaths/min, and oxygen saturation of 100% on room air. She denied palpitations, shortness of breath, light-headedness, or chest pain. Her neck was supple without a palpable goiter or nodules. She did not have a tremor. She was alert and oriented to time, place. She endorsed feeling depressed and hopeless which had led to the attempted suicide but now felt remorseful for the attempt. Laboratory workup was notable for lithium level 0.24 mEq/L (0.50 – 1.20 mEq/L), potassium 3.3 mEq/L (3.6 – 5.1 mEq/L), and a negative urine toxicology screen. Electrocardiogram showed normal sinus rhythm without evidence of T-wave abnormalities. Thyroid function tests revealed a thyroid stimulating hormone (TSH) of 1.087 µIU/mL (0.350 – 5.500 uIU/mL ), total T3 of 360 ng/dL (80 – 180 ng/dL), and free T4 of 11.76 ng/dL (0.8 – 1.80 ng/dL).
She was admitted with suicide precautions and initially treated with lorazepam as needed for anxiety. She developed tachycardia of 101 bpm on day 3 and atenolol 25 mg daily was started. Her heart rate remained in the 80 – 100 bpm range until discharge. Her free T4 trended down into the normal range on day 15 of admission and levothyroxine 50 mcg daily was restarted. She was transferred to the inpatient psychiatric unit for further management of her depression.
Discussion: Prior reports have described a benign course after overdose however symptoms may present in a small subset of patients. These symptoms can be mild (tremors, tachycardia, restlessness, headaches, vomiting) or severe (transient hemiparesis, coma). More severe symptoms have been described with higher doses ingested (levothyroxine 75000- 125000 mcg). Therefore, obtaining history and collateral information about the total dose ingested is important. Free thyroxine levels are trended for biochemical follow up and commonly return to normal after two weeks. TSH levels may remain suppressed well beyond the two-week period and therefore are of limited use in an acute setting. Treatment options include close clinical follow up with symptomatic treatment for tachycardia with beta-blockers. Development of severe symptoms may require levothyroxine extraction through hemodialysis or plasmapheresis.