Thyrotoxic periodic paralysis - a retrospective study from Southern India.

Objective: Thyrotoxic periodic paralysis is a rare manifestation of thyrotoxicosis. Here, we describe the clinical and biochemical features and treatment outcomes of this disorder.

Methods: This retrospective study was conducted at a tertiary care centre in southern India. The clinical and biochemical features, treatment received, and therapeutic outcomes of all patients with thyrotoxicosis and acute flaccid paralysis without any other identifiable causes (cases for the study) were compared with an equal number of consecutively selected patients who presented with thyrotoxicosis but without features of paralysis (controls for the study) during the same period.

Results: In total, 41 cases and controls were included in this study. The proportion of males was 92.6% and 43.9% in the cases and controls, respectively. The mean age was 32.8 (±7.6) years (cases) and 39.7 (±11.3) years (controls). In the cases, 20% of patients presented without clinical thyrotoxic features. Graves' disease was the most common aetiology of thyrotoxicosis in both groups (92.6% of cases and 87.8% of controls). The prevalence of goitre was significantly higher among controls (90.2%) than among cases (53.7%). The mean serum potassium, free T4, total T4 and total T3 levels were significantly lower in the cases than in the controls. In these cases, two patients had an additional aetiology for persistent hypokalaemia, likely Gitelman's syndrome.

Conclusion: This is one of the largest series of thyrotoxic periodic paralysis cases in India. In subjects with thyrotoxicosis, serum potassium, free T4, total T4 and total T3 levels were significantly lower in those with periodic paralysis than in those without.