Severe hyponatremia due to ACTH insufficiency in a 14 year-old girl with growth hormone deficiency.

SIADH-like hyponatremia as the presenting manifestation of ACTH deficiency is rare in childhood. Here we report a 14 year-old girl who, after 8 years of GH replacement and subsequent treatment for subclinical secondary hypothyroidism, presented with confusion and disorientation due to severe hyponatremia. When her pituitary axis was re-assessed, she was diagnosed as having ACTH deficiency associated with multiple pituitary hormone deficiencies (MPHD) (including GH, FSH, LH, and subclinical TSH deficiencies). She responded poorly to treatment with only hypertonic fluid, but improved after addition of hydrocortisone replacement. The purpose of this paper is to emphasize the importance of suspecting ACTH insufficiency in children with GH deficiency if hyponatremia develops.