Favorable functional outcomes in acute ischemic stroke patients with subclinical hypothyroidism

To investigate the protective effects of subclinical hypothyroidism (SCH) on ischemic stroke severity and its functional outcome.

Seventy-three consecutive patients admitted for first-ever cerebral ischemic stroke who met the inclusion criteria of this study were included. Serum thyroid-stimulating hormone (TSH) levels were measured for all patients. Stroke severity was recorded for each patient on admission using the NIH Stroke Scale. The patients were followed, and their functional outcomes were evaluated at 1 and 3 months after stroke using the modified Rankin Scale (mRS) and the Barthel Index. All values were compared between patients with and without SCH (serum TSH in the range of 2.5-10 mIU/L, with normal thyroid function test results).

Of the patients, 49 (67.1%) had normal serum TSH, and 24 (32.8%) had SCH. Patients with higher levels of serum TSH tended to have a milder stroke on admission with a significantly better outcome, described as a mRS score of 0 or 1, at 1 (p = 0.029) and 3 (p = 0.048) months of follow-up. Mortality was also found to be lower in the group of patients with SCH (p = 0.008, at 3 months of follow-up).

This study showed a significant protective association of SCH with better outcomes and lower mortality after cerebral ischemic stroke. Possible explanations for this association are ischemic preconditioning, reduced adrenergic tone, and hypometabolic state.