Abstract
Hyponatremia is a common clinical condition in patients with severe motor and intellectual disabilities. In the 104 institutionalized patients at our center, there were 11 patients (10.6%) with chronic hyponatoremia. This study analyzed the hormone secretion, water and electrolyte balance, and underlying diseases in 9 patients whose detailed data were available. Seven out of 9 subjects showed the syndrome of inappropriate antidiuretic hormone secretion (SIADH), but only one subject presented with a serum ADH level above the measurement sensitivity level. All subjects took carbamazepine (CBZ), which could be responsible for the occurrence of SIADH without any excess ADH secretion, and it could also be involved in these hormone, water and electrolyte conditions. Regarding the underlying disease in these subjects, there were 4 subjects with hypothyroidism. However, no subject demonstrated cerebral salt wasting (CSW). CBZ is one of the underlying diseases most commonly associated with chronic hyponatremia in patients with severe motor and intellectual disabilities, and hypothyroidism could thus be related to its development.
