SUN-563 TSH Elevation after Seizure: An Underappreciated Cause of Nonthyroidal Illness Syndrome

Introduction: TSH is commonly assessed at hospital admission to exclude thyroid dysfunction as the cause of a patient’s presentation. However, thyroid function tests (TFTs) are commonly altered as a result of the condition leading to the presentation, referred to as nonthyroidal illness syndrome (NTIS). Thus, it is often difficult to interpret the true meaning of abnormal TFTs in hospitalized patient. In fact, hypothalamic-pituitary-thyroid axis can be altered in up to 75% of hospitalized patient (1). Typically, the TSH in NTIS is normal or low, but can temporarily rise above normal as the patient recovers from NTIS (2). We present the case of a patient who had significant TSH elevation immediately after a prolonged seizure. Clinical Case: A 93-year-old female with past medical history of seizure disorder on Levetiracetam, presented with a prolonged seizure. Her blood count, metabolic profile, and Levetiracetam level were all unremarkable. There were no acute changes on a noncontrast head CT. Her only notable test result was TSH 26.30 MIU/L (normal range 0.27-4.20 MIU/L) with a Free T4 1.2 ng/dL (normal range 0.9-1.7 ng/dL). She had no prior history of thyroid disease or family history of thyroid conditions. Endocrinology was consulted for the interpretation of her TFTs. The differential diagnosis included subclinical hypothyroidism and NTIS. TSH and Free T4 were rechecked two days later and were then both within normal range. The patient was diagnosed as euthyroid with transient TSH elevation due to seizure. Conclusions: The case highlights, generally, that TFTs can be unreliable in an acute illness, and that seizures may cause an acute, transient rise in TSH. In our case, the patient’s TSH elevation, occurring after a seizure, normalized on repeat testing two days later. In studies on TSH levels following ECT-induced seizures in depressed patients, researchers demonstrated transient TSH elevations (3). Wada et al. reported a similar case of a patient with non-convulsive status epilepticus with TSH elevation that normalized spontaneously (4). We advise that the diagnosis of subclinical hypothyroidism not be made in a patient presenting with a recent seizure, as the seizure itself may be the cause of elevated TSH. As with most cases of NTIS, follow up over time may reveal that the patient is, in fact, euthyroid. References: (1) Ganesan K, Wadud K. (2018). Euthyroid Sick Syndrome. In: StatPearls. Treasure Island (FL) (2) DeGroot LJ. (2001). The Non-Thyroidal Illness Syndrome. In: Endotext. South Dartmouth (MA) (3) Dykes, S., Scott, A., Gow, S., & Whalley, L. (1987). Effects of seizure duration on serum TSH concentration after ECT. Psychoneuroendocrinology, 12(6), 477-482. (4) Wada A, Suzuki Y, Midorikawa S, et al. (2011). Thyroid-stimulating hormone elevation misdiagnosed as subclinical hypothyroidism following non-convulsive status epilepticus: a case report. J Med Case Rep., 5:432.