Changes in plasma renin activity and plasma aldosterone in the induced paralytic attack of thyrotroxic periodic paralysis.

Changes in serum electrolytes, haematocrit, plasma renin activity and plasma aldosterone induced by glucose and insulin (GI) infusion were serially investigated in seven patients with periodic thyrotoxic paralysis. An attack which developed into complete quadriplegia was induced within 90 min after the beginning of the GI infusion in four out of seven patients. Only a slight paralysis of the legs was produced in another two patients and induction of an attack did not materialize in one. In four patients with complete quadriplegia, the mean values of serum sodium and potassium concentrations, haematocrit, plasma renin activity and plasma aldosterone slightly decreased immediately after the beginning of the GI infusion. Induction of a paralytic attack was not accompanied by any significant changes in serum sodium concentration, haematocrit, plasma renin activity and plasma aldosterone either 15 min before or after the onset of attack, while the serum potassium concentration progressively decreased, and an increase in plasma aldosterone associated with an increase of haematocrit and plasma renin activity reached a peak level at the stage of complete quadriplegia. On the other hand, in the three patients in whom an infusion produced slight or no paralysis of the legs, changes in the serum sodium concentration, haematocrit, plasma renin activity and plasma aldosterone were insignificant and the serum potassium concentration was slightly but insignificantly decreased. These results suggest that hyperaldosteronism may not be a trigger for the induced paralytic attack but a phenomenon secondary to volume depletion and a change in potassium homoeostasis induced by GI infusion.