Dr K K Aggarwa
Rajesh, aged 40 years, one of my employees with confirmed H1N1 flu developed persistent tachycardia, hypotension, restlessness and air hunger. He was managed conservatively in the ICU. Tachycardia was controlled with Ivabradine. But, tachycardia was persisting even after discharge.
We investigated him further. Thyroid profile revealed TSH to be 0.004 suggestive of acute thyroid storm, which was quite possibly precipitated by H1N1 flu.
We carried out a literature search for evidence showing an association between the two. Much to our surprise, there was evidence-based data supporting this association. Cases have been reported of thyroid storm triggered by H1N1 infection.
A case of 31-year-old female with H1N1 precipitating thyroid storm was published by Salim Alawi Baharoon in April 2010 issue of the Annals of Thoracic Medicine. The patient presented with history of high-grade fever, vomiting, productive cough and increasing shortness of breath. She was given empiric antibiotics and oseltamivir along with other treatment. Unexplained tachycardia prompted thyroid function tests, which were suggestive of a diagnosis of thyroid storm (Ann Thorac Med. 2010 Apr;5(2):110-2).
A similar case of H1N1 infection accompanied by thyroid storm was published by Oguz et al in 2010 in Endocrine Abstracts (Endocrine Abstracts. 2010;22:194).
A thyroid storm is a rare life-threatening exacerbation of thyrotoxicosis, and is usually characterized by hyperthermia, tachycardia, severe agitation and altered mental status. It is a medical emergency and carries a mortality of 10%.
Thyroid storm is often precipitated by interruption of thyroid medicine use, acute medical illness, trauma or surgery. Systemic infections such as respiratory infections, endocarditis and urinary tract infections have been known to precipitate a crisis.
The diagnosis of thyroid storm mainly depends on the clinical presentation and results of thyroid function tests. The thyroid stimulating hormone (TSH) level will be abnormally low or even undetectable, and the levels of T3 and T4 will be elevated.
Diagnosis may be delayed due to the nonspecific clinical presentation.
Patients who have survived thyroid storm should receive definite therapy for their underlying hyperthyroidism to avoid any recurrence of this potentially fatal condition.
Although literature does not conclusively establish a cause and effect association between H1N1 flu and thyroid storm, it is still important to know the clinical signs and symptoms of thyroid storm and the condition should be kept in mind as differential diagnosis in patients with unexplained tachyarrhythmia, alterations of consciousness or hypermetabolic status.