[Myxedema coma with hypervasopressinism. 2 cases].

Hyponatremia is usual during myxedema coma. Hereafter we report two cases with increased plasma arginine vasopressin (AVP). Patients were admitted because of hypothyroid coma. In each case, there was an hyponatremia with normal urine sodium and low serum osmolality. Renal function was normal. On hormonal results, primary hypothyroidism was evident. Plasma AVP was increased. The plasma cortisol of one patient was high. Immediate therapy associated: water restriction, hypertonic saline infusion, furosemide, oral thyroid hormones with low doses. On the fourth day, conscience improved obviously. Natremia and plasma AVP went back to normal state before returning to euthyroid state. Patients went on improving along with normalizing thyroid status. Hyponatremia can be a serious sign of hypothyroidism. In case of myxedema coma with hyponatremia, clinical improvement seems to be related to fast correction of water and electrolyte disturbances and we prefer to give low doses of thyroid hormones at first. The hyponatremia and increased plasma AVP mechanisms are complex. However, in each of these cases, plasma AVP come back to normal before returning to euthyroid state. In one case, high plasma cortisol level rules out adrenal insufficiency as causal mechanism of electrolyte disorders.