A fairly astonishing overdose of levothyroxine - with very little impact. Massive overdoses seem more common in children and, thankfully, they very often have little impact. Massive overdoses in adults are often far more serious.
We could speculate that the worst impact might be in someone who has a high capacity for converting T4 to T3. In children, this might be more restricted. Perhaps the individual in this case simply couldn't convert fast enough to cause the usual effect of overdose?
Medicine (Baltimore). 2018 Jun;97(23):e10909. doi: 10.1097/MD.0000000000010909.
No obvious sympathetic excitation after massive levothyroxine overdose: A case report.
Xue J1,2, Zhang L1,2, Qin Z2, Li R2, Wang Y2, Zhu K2, Li X3, Gao X4, Zhang J5.
Author information
1 Department of Urology, The Second Affiliated Hospital of Southeast University.
2 Department of Urology, The First Affiliated Hospital of Nanjing Medical University.
3 Department of Urologic Surgery, The Affiliated Cancer Hospital of Jiangsu Province of Nanjing Medical University.
4 Department of Oncology, The First Affiliated Hospital of Nanjing Medical University, Nanjing.
5 Department of Urology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China.
Abstract
RATIONALE:
Thyrotoxicosis from an overdose of medicinal thyroid hormone is a condition that may be associated with a significant delay in onset of toxicity. However, limited literature is available regarding thyrotoxicosis attributed to excessive ingestion of exogenous thyroid hormone and most cases described were pediatric clinical researches. Herein, we presented the course of a patient who ingested a massive amount of levothyroxine with no obvious sympathetic excited symptoms exhibited and reviewed feasible treatment options for such overdoses.
PATIENT CONCERNS:
A 41-year-old woman patient with ureteral calculus ingested a massive amount of levothyroxine (120 tablets, equal to 6 mg in total) during her hospitalization. Her transient vital signs were unremarkable after ingestion except for significantly accelerated breathing rate of 45 times per minute. Initial laboratory findings revealed evidently elevated serum levels of thyroxine (T4) >320 nmol/L, free triiodothyronine (fT3) 10.44 pmol/L, and free thyroxine (fT4) >100 pmol/L. The patient had a history of hypothyroidism, which was managed with thyroid hormone replacement (levothyroxine 100 μg per day). Besides, she also suffered from systemic lupus erythematosus and chronic pancreatitis.
DIAGNOSES:
This is a case of excessive ingestion of exogenous thyroid hormone in an adult.
INTERVENTIONS:
The interventions included use propranolol to prevent heart failure; utilize hemodialysis to remove redundant thyroid hormone from blood; closely monitor the vital signs, basal metabolic rate, blood biochemical indicators, and serum levels of thyroid hormone.
OUTCOMES:
The woman had no obvious symptoms of thyrotoxicosis. After 4 weeks, the results of thyroid function indicated that serum thyroid hormone levels were completely recovered to pre-ingestion levels. Accordingly, the levothyroxine was used again as before.
LESSONS:
Adults often exhibit more severe symptoms after intaking overdose levothyroxine due to their complex medical history and comorbidities than children. As for them, hemodialysis should be considered as soon as possible. Besides, diverse treatments according to specific symptoms and continuously monitoring were indispensable.
PMID: 29879029
DOI: 10.1097/MD.0000000000010909
Bloods after starting Levothyroxine
Feeling hot after levothyroxine
Exhaustion after starting levothyroxine 
Nervousness after levothyroxine
